Low Boost Issue - Please Help

[Hedge]

Recently I had my 87 GN in the shop for the following. Replacing crank sensor, front and rear main seals, oil pan gasket, timing chain cover gasket and timing chain. I had some serious oil leaks.

Before I put the car in the boost PSI was 17 - 18.
After I got the car back the boost goes to about 13 PSI max.

It also seems sluggish to build boost from a stop. If I am doing 55 plus the boost builds almost like normal.

Any suggestions where I could look for the cause?

Everything is stock.

 

[ringman]

is it possible there is an exhaust leak, from when they may have taken the crossover pipe off?

 

[stack1]

Who did the work, do they specialize in turbo Buicks? Sounds like an exhaust leak to me since you're able to boost fine at higher speed when there's enough exhaust to overcome the leak.

 

[Hedge]

That is definitely a possibility. I don't hear an exhaust leak but I guess that doesn't mean there is not one. This is my normal mechanic but he is reliable and good at what he does even though he is not a Buick specialist. I guess I need to check the gaskets and where the pipe meets underneath.

Any other ideas in case this is not it?

 

[stack1]

I'm thinking it's gotta be an exhaust leak. It it were a boost line, you wouldn't be getting any at highway speed. You won't normally hear a leak because it will only happen under boost and that means you're in your car with wind and engine noise. Find out if he took the headers off the heads, hopefully he didn't and you only need to check the crossover pipe.

 

[BlackBandit]

Check to make sure they hooked up your wastegate properly. 13 PSI sounds like you're running spring pressure for boost.