I've been trying to figure out this boost problem for about a year now. When I first got the car the boost pattern was perfect (10-8-10). About a week after getting the car the coupler on the y-pipe blew off and I've had problems since. The coupler was replaced and reinstalled but now the boost pattern is 11-8-11 and then immediately after the transition the boost slowly drops and bounces around from 5-9 psi to red line.

I'm thinking its the pills in the vac lines but don't want to spend money blindly. Any advice is appreciated.

 

bump.

could it be bov?

 

BOV could be leaking, also could be leaking somewhere else if it blew off one, others could be leaking. There are so many places it could be I would get a vacuum tester and pressurize the sytem and start from there to see if you have any lines leaking.

 

if you've not replaced your vacuum lines yet, now is probably an ideal time. if you're going to spend all the effort and time/money searching for a possible leak, you might as well just go ahead and upgrade them all, fixing any leaks in the process without having to search for one specific line. considering the max boost before and after transition is the same, i'm guessing it is not the BOV or it would be causing that problem before it too.

to me, it sounds like there is a leak in a vacuum line that is only pressurized when the secondary turbo comes on-line. (i don't know the system by heart though, so this may never actually happen, check out the vacuum line diagrams).

if you are going to serach for vacuum line leaks, do a search in the 3rd gen section as there are a number of threads (IIRC) with tips about how to find leaks.

good luck.