I have the same problem, but only when the motor is cold. I thought it was a boost control issue, but I don't think it is anymore. Then I thought tip-in enrichment, but I realized it mainly happens well after a throttle position change.
Quite a few of us have been experiencing this after going stg 2.
I have also suspected the timing belt. They stretch over time with load, I'm at 77k miles, I wonder if it has stretched a bit or skipped a tooth or something. After a reflash, it runs like crap for a couple of minutes. Someone else on the board experienced that and when they did the timing belt, it had skipped a tooth or two.
I'm looking for ideas too!
__________________
Scott
04 MT FXT STG 2 5 spd
02 WRX STG 2 5 spd
|