Underboosting Evo 8
 

Where should I start checking, here are the symptoms of the problem;
-MBC set at 20psi is now hardly doing even 18psi, mostly just 16. :crap:
- Idle AFRs read 11s and redlines to 9s rather than 14.7 to 11.4 (running rich) :confused:
- after letting of the throttle and the bov sets off, there is a slight hissing sound that comes. this sound is not from the bov as my bov has already set off by then and I am using a turbosmart recirculative valve.

I feel like this is a problem that has gotten worse because I was never able to exceed 22psi, dont' know why, I am on the stock 2003 evo 8 turbo..

:helpme::helpme::helpme::helpme:

Certainly a boost leak test is in order? (hissing sound)

check all vacuum lines esp those on the EGR solenoid behind the manifold. Check the lines on the turbosmart BOV and zip tie everything !!.

Then do the boost test. :-)

It's probably got something to do with this one?

https://www.evolutionm.net/forums/ev...smell-gas.html


Probably a hole in the intercooler.

Boost leak almost forsure, do a boost leak test

Update
 

Make sure to put seals in freezer until you are ready to pop into place. Also, do not remove any of the black tar on back of throttle plate or you will have high idle.

Now for the weird 11 AFR of at idle. Idle isn't boosting, so there isn't any pressure to leak out. Unless the 11 AFR is with engine cold where it hasn't switched to closed loop. If engine was warm when you got 11 AFR, I think this will still be there. Hope I'm wrong.