Interesting BUT the AA450 has always been the part number for the FSTIThey are the same thing. 211 is a superseded part number.
AA450 is not specific to FSTI, it's the same part number for FXT, WRX, STI, etc. It's just a new part number. I have the Denso above on my FXT.
You're right, I should clarify they've recommended this one as a replacement when it fails as happened when I bought my '04 FXT with the P0420 code and consulted our local tuner. The Denso went on that one, and it's gone on my 07 FXT as a preventative measure at 60k milesI would suggest narrow band is not great for tuning. wide band is a much better option..... if your talking tuning and you are.