I have a question on a vacuum leak issue. I have replaced the UIM and LIM, a new PCV valve and MAP sensor and there is a slight hissing sound coming from the engine now. I have read other posts and I do have all the o-rings replaced and all is snug. Now I was looking at the illustration in my service manual and it appears that there is a spring in the PCV housing. I did not notice a spring from the old original UIM and did not recieve one with my new one from APN, is this spring necessary? I let the car idle and removed the oil fill cap and it almost stalled but recoups and continues to run. I read B. Buttermore'* post on a vacuum issue : (We had an L27 with a nasty vacuum leak to the crankcase caused by failed LIM gaskets - I don't doubt that the L36 could do the same.) I just changed the LIM gaskets and sealed them pretty good w/ silocone whats the probability there is a leak and if so how can I locate it ?

Spray throttle body cleaner around the LIM, UIM and throttle body gaskets, as well as any vacuum fittings. Check the EGR tube from the EGR valve to the LIM also.

I recently did my UIM/LIM work, and noticed my vacuum lines were getting dry-rot.

I made a trip to the parts store and took care of it. Runs smooth now.
Advance Auto has a package of 7/32" tubing that can do the whole car and then some.

Give it a try.
Bob

Take the pcv valve back out and make sure there in only one o-ring on the bottom. Shine a really bright light in the hole. You have a vacuum leak to the crankcase, and that is almost certainly the cause.