I just installed an ottp stage kit (2.8, 60's) on a friends cobalt, he upgraded from GM stage 2.

We flashed the tune they sent us, and now his car won't make any boost above 4 ibs. I'm guessing this is residual boost that the solenoid can't bypass (i.e I think it's trying to bleed all boost).

After checking vacuum lines i realized the previous owner had done some form of the boost bypass mod which he hadn't realized.

We are going to pick up some vacuum hose and undo that, any other suggestions on what could be going on?
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fix the boot actuator hoses, and connect the boost solenoid properly, put the car back to make it correct and all will be well I bet.

 

We sort of fixed the boost bypass, the auto parts store didn't have a correct size vacuum hose.

We switched the GM stg II tune back on and boost was fine, so the problem was the tune not the bypass mod or anything mechanical.

After looking over the tune I saw a couple of weird things and changed them (max % boost was set to 200 instead of 100... and integral gain for boost was set to .1 instead of higher than the proportional gain .5 )

After changing those issue solved, must have been a mishap when they were making the tune or accidentally adding a value instead of making it equal to.