1987 T2
89,xxx miles

I noticed this problem after I removed my airpump and ACV and added the cover plate.
It may not be the cause but here's what happened.
My low end torque went down. I do still feel it being torquy after 4k RPM.
And when I'm inside my car, I hear a resonating high pitch sound once in a while coming from the passenger side of the engine. Sometimes it's there sometimes it's not.

It's like my car lost power.. I'm not feeling like it launches like it used to do.

 

sounds like you have a boost leak.
Did you use silicone or a gasket with that block off plate?

 

I used a gasket.

 

Check the vacuum line that feeds the twin-scroll actuator. It's the canister attached to a linkage on the turbo manifold and has a hardline going towards the rear of the engine.

 

I'll check it out. But I'm not sure about it if it's causing my problem. I feel like it has something to do with the ACV cover plate or something on the UIM.
There' were metal pipes connecting to the ACV, does boost leaks happen there if its not covered?