My car keeps throwing code 33 which is low vaccum. I replaced the Idle Air Control, EGR gaskets, and checked all my vaccum lines. I still can't figure this out. Anybody have suggestions where to look. I did change my intake to the TPI style with the 2 air filters in front/above the the radiator but I don't think that should matter. Anybody have a suggestion. I am starting to get pissed because i need this car running well.

 

MAP sensor shot?

Have you checked the voltages to and from the MAP sensor?

GRY wire should be 5V Ref
Black wire is GND
Lt Grn wire is signal to the ECM(~2V KOEO)

 

How do I test the MAP sensor?

Do I measure the voltagewith the connector on the MAP sensor or off?
Engine running or not?

I replaced the MAP sensor, but I'm still getting odd behavior.
(codes 33 and 34s)

 

I had the exact same problem...
https://www.thirdgen.org/forums/v6/3...code-33-a.html

After basically giving up, I took it to a shop...they used a smoke injection tool they just got from a GM rep and they said it was leaking "all over the intake manifold". They replaced those gaskets and it seems to have cleared up the code 33 problem (which for me was causing it to not idle down when driving and lifting -not until it got below 10 MPH when the computer would apparently over-ride the vacuum reading which was making it think there was a load on the engine).

I guess I really did have a low vacuum situation...it must have been leaking so badly that I wasn't hearing any hissing noise or anything...