Major loss of power under boost

[94SCblack5speed]

Every time i step on the gas pedal and give the car more than 3-4 lbs of boost i feel a shaking sensation and alot of vibration. I have to let off the gas just to get the car to accelerate it seems. Car has about 158k on it any suggestions would be appreciated. I just replaced plugs/wires and its still having the same problem.

[David Neibert]

Sounds like a fuel delivery problem. The fuel filter, fuel pressure regulator (not increasing pressure) or the fuel pump could cause those problems.

Start by looking at the regulator and make sure the vacuum hose didn't fall off. Then buy or borrow a test gauge...with vac line off the regulator you should be getting between 38 and 40 psi on the rail. With vac line attached it should show about 35 psi at idle and pressure should increase with manifold pressure.

Poke the throttle hard enough to get into boost and confirm that fuel pressure is increasing pound for pound with boost. 10 pounds of boost should result in 50 pounds of fuel pressure. With a weak pump or clogged filter you will not be able to maintain flow and pressure when in boost and the fuel pressure reading will begin to fall instead of raise.

David

[SC UL8R1990]

also check the clamps on your air intake hose. My intake tube fell off the throttle body and had the same exact symptom as you.

[Deep6]

It wasn't fuel or intake or spark probs.

Instead it was a clogged exhaust. Hopefully that isnt your problem, but it could be partially clogged up. I had a severe loss of power in my 95-5spd. Hollowed the cats out and it solved the prob.