Hey guys... well i just got my engine completely rebuilt... after the break in and final check, everything was working fine... the boost patterns were perfect...

now a few days later... im noticing my boost pattern has changed a bit... it goes 10-8 and stays at 8... my mechanic said i have a small exhaust leak.. could this be the culprit? when driving i can hear and feel the second turbo come online.. but the boost doenst go back up to 10 it stays at 8 to 8.5ish 9ish, but definitely not back up to 10..

any help or suggestions would be great

 

Maybe rear turbo is on its way out? Do you notice any oil leaking into your exhaust possible some smoke on start up that smells like oil? If you have a lot of miles on them. Thats just the obvious easy answer, I'm sure a vet will come in with something to dwarf my idea

 

I had that problem too. Even with a greddy pofec b spec 2 boost controller, mine would drop off to about 8 or so and I was pushing around 13 psi, it would pull good until it hit about 4 grand or so and just drop to eight and stay there, especially on the highway it was almost instantaneous. And it was a boost leak ( a very small one) but it did it. And like he said ^, check for oil coming out of your secondary turbo. I would check your gaskets on the y pipe and secondary turbo pipe that leads to your intake. sometimes those little metal gaskets blow. un fortunately if all of your gaskets are still good and you still have a leak there is a chance you'll have to rebuild them, or make your dreams come true and go single! I just did and it is orgasmic

 

Exhaust leak - possible, but very unlikely to affect boost.
Blown secondary - very unlikely, unless it's blowing a lot of oil or making a load of exhaust smoke.

Boost leak - check this first - check every coupler from the y-pipe to the throttle elbow by removing them from the car and flexing them to find small cracks.
Loose or misplaced vacuum hose - second thing to check for. Also be sure the check valve between the pressure tank and y-pipe is not leaking and has the arrow pointed toward the tank.

 

I had a similar problem accompanied by a whistle when the second turbo came online, turned out the y-pipe wasn't bolted to the output of the second turbo. Almost impossible to see from above so I didn't find it until I felt around with my fingers.