From what I've read the stock boost on an 05 VIII is 20.3 PSI. Last night I hooked up a boost gauge and she's only hitting 12 PSI. I got my Evo with 34k on it from a dealership in Houston TX not knowing what all mods had been done to it. I'm trying to get ahold of the previous owner to find this out. So far what I've seen is that the boost control solenoid has been moved up to the side of the airbox and the lines have been zip-tied on to it so the restrictor has been removed. Can removing the restrictor cause the boost to drop? I have an MBC to hook up to raise it back up however is there anything else I should check for that can cause the stock level to drop?

Thanks!
Matt

 

Stock boost level is 19.5 , Yes you need the restrictor pill that goes in the boost line from the turbo nipple to the boost solenoid if your not running a MBC . I would just hook a MBC and see if you can get it too boost to 20 psi.

Another issue may be a boost leak . Get a boost leak tester and see if any air is leaking out at the couplers and pay close attention to you Throttle body seals . I had a 05 EVO that a bought brand new and after 6,000 miles my TB seals where shot ... I replaced those and car hauled *** once again . You can find the TB seals on Mach V website and there is some "DIY" articles on here on how to change them out but its very simple .


hope that helps a little

 

I come from a 90 4G63 TSI so I'm well aware of the leakage issue, just hoped since it was only 2 years old it wouldn't be an issue but I know that's not a valid point as I don't know what the guy did to the car. On another note I hooked up the MBC and all appears well with it holding 19 lbs, guess it reverted to wastegate base but it's back to usual now. Huge difference from 12 to 19 lbs Thanks for the words of wisdom!