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Premium Member
2007 XT Sport 5MT
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04 FXT, 61 Stude
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1,742 Posts
What year is the Forester? If it's 04-05 I'd recommend getting a catless uppipe if you plan on going stage 2 with the VF39 (lucky). You don't need the catback for stage 2, but I just love the rumble way too much.
 

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Premium Member
04 Acura TSX the slick 6 speed
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2,395 Posts
You can get a Helix DP which is just as good, new for under $400, used even cheaper. Then use used STi parts for the rest of the exhaust and you'll come out about the same, but it will cost you about half as much.
 

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Official sf.org decal guy
2006 FXT
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12,516 Posts
Forgive my ignorance but isn't bigger better on a turbo? STi is only 2.5" when it might be more beneficial to go 3".
Well fun fact; the Cobb TBE isn't a true full 3". At the DP/mid-pipe junction there is an area that is 2.5". However this small area is commonly modified as I have done it on mine to get a true 3" from turbo to exhaust tip. I also modified mine with a flex joint.

I have a Cobb catback and LOVE LOVE LOVE the sound. I would be surprised if they actually had one though. Most resellers just post up the items and then they are drop shipped. Call and find out. If you have the money i would definitely recommend the Cobb TBE
 

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9,011 Posts
Forgive my ignorance but isn't bigger better on a turbo? STi is only 2.5" when it might be more beneficial to go 3".
The piping after the downpipe doesn't have much effect on power until you get to a much bigger turbo than a vf39. The downpipe+tune gives most all of the power benefits. BTW, the OTS maps aren't great, I'd definitely get a custom/protune if you're going to anything beyond just a downpipe (especially a nonstock turbo).
 

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Premium Member
04 Acura TSX the slick 6 speed
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2,395 Posts
The piping after the downpipe doesn't have much effect on power until you get to a much bigger turbo than a vf39. The downpipe+tune gives most all of the power benefits. BTW, the OTS maps aren't great, I'd definitely get a custom/protune if you're going to anything beyond just a downpipe (especially a nonstock turbo).
I agree with all of this, but the OTS maps are OK for a time, don't feel like you have to rush out and spend all this money at once. If money allows, get all the parts and tune at once, but if not, you can get by fine on the OTS maps. The Cobb maps worked really well on my car, my custom tune improved things but my tuner (Doug Wilks @ TopSpeed) was impressed with how well the OTS did for it.
 

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Ol' Timer
2006 WRX Spec-C 6MT
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6,091 Posts
I would like to keep the cat. I'm a bit of a treehugger.

It's an 04.
He's talking about the pre-cat. The cat that's in the up pipe does very little to reduce emissions. It is mainly used to reduce emissions before the secondary cat warms up. The biggest problems with it are that it reduces spool by restricting airflow to the turbo, and it is known to break apart and shoot chunks of metal into the turbo and destroying the fins. All 06+ turbo Subies have no more pre-cat.
I have also kept my secondary cat because of emissions concerns.

Forgive my ignorance but isn't bigger better on a turbo? STi is only 2.5" when it might be more beneficial to go 3".
You need a 3" downpipe in order to go to stage 2, either on the stock turbo or the VF39. A 3" cat back helps increase flow and frees up some additional power, but it does come with a penalty in sound (unless you like the sound, which I do). There are some quiet 3" catbacks available from MadDad.

The Cobb maps worked really well on my car, my custom tune improved things but my tuner (Doug Wilks @ TopSpeed) was impressed with how well the OTS did for it.
You know, they have been excellent on my car too. Both the Cobb stg 2 and the Cobb VF39 map have been awesome. When they took a look at the dyno plot and A/F ratios they (Cobb) told me they can do very little to improve on it. Sure there's some power to be had, and having multiple maps would be great, but I can wait for a little while.
 

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Official sf.org decal guy
2006 FXT
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12,516 Posts

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Premium Member
'09 STI
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4,212 Posts
OK. My goal is to run this map: http://www.accessecu.com/accessport/subaru/new/04 FXTM/Map Notes/FXTVF39+STiIC 91MTv101.pdf


Would a simple 3" catless downpipe with stock catback suffice with a STi TMIC and VF39?
Can't comment on shelf tunes but that pretty much covers it. You don't really need the TMIC but it will help. I'd give the map provider a call to be sure. They'd know better than anyone.

I don't want a loud car. Just power.......and women
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"In dis country, first ju godda make da money. Then after ju make da money then ju get da power, then after..."
 

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2004 Forester XT 5spd
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237 Posts
Discussion Starter #17
Can't comment on shelf tunes but that pretty much covers it. You don't really need the TMIC but it will help. I'd give the map provider a call to be sure. They'd know better than anyone.

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"In dis country, first ju godda make da money. Then after ju make da money then ju get da power, then after..."
I'm glad someone picked up on that reference.
 

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Premium Member
2017 VW Golf SportWagen 5MT
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10,887 Posts
Yeah, just the 3" downpipe will be fine for running OTS Stage 2 maps. You can search cobbforums and find posts mentioning that. I recently upgraded to a full 3" exhaust and the power difference isn't very noticeable, at least without a re-tune. I was always able to hit target boost without issues before. What IS noticeable is sound -- the car is LOUD. This is with the MadDad Whisper, which supposedly is the quietest option out there.

So, unless you like the sound, just get a catted aftermarket downpipe. I had a Cobb before and am running v4 Invidia now, both are great quality. Cobb has an O2 bung in the bellmouth if you wanted to install a wideband, Invidia does not.

Stan
 

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2008 FSXT M/T
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4,170 Posts
another cobb tbe owner who loves his exhaust. the sound, fit and finish, and looks are unrivaled! i still have the taper down to 2.5" then back to 3" again w/ no ill side effects. mine is also catted, wouldnt have it any other way. must be my old age LOL, but this is the first catted subie ive ever had, i got sick of the stinkyness... but youll def want a new catless uppipe, not only for power - but godforbid it craps the bed and sends the broken pieces through your turbocharger!
 
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