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Running rough...MAS?

I took off the air can which housed a K&N cone filter yesterday. Since then, the car has ran pretty rough. It's much louder (not the good kind). I'm getting boost, but the car is pretty flat and loud. One thing I did notice which may or may not be relevant is that the stock boost gauge is not reading as close to my Apex boost gauge as before. Namely, I wouldn't get the 3 bars of vacuum when I started to hit boost like I did before. Is there a way I can test the MAS (stock) or see something in the logs? No CELs so far.

Before the air can work, the car was running a bit flat, but it was not loud like this.



Well-known member
^+1 Plus, try not to hit boost until you get this figured out. You're most likely running lean. Boost leak test is best if nothing apparent. What does your A/F meter show?


Well-known member
Oversensitive knock sensor? Sounds like you need a boost leak test and to log your car. I could be a few things, but I'd check those first.

Turns out it was a blown down pipe gasket. Got it fixed and also replaced the dented 3" downpipe with a 2g Greddy.