[.Jack.]

Originally Posted by Jamesp

I found a super way to find a vacuum leak, or completely rule one out while trouble shooting a SAI problem. It's a bit involved, but bullet proof.

First roll the engine to TDC. (That's the first part of involved)

Then pull the plastic intake tube off the throttle body and slip a 3 mil piece of plastic between the tube and throttle body, put the tube back on the throttle body (the second part of involved)

Pull a vacuum hose off the intake manifold and blow into it. The manifold should hold air. It should feel like you are trying to blow up a hot water bottle. When you release the air, it should blow back out the hose. Holding my finger over the hose, my intake held pressure for about two minutes. Pretty impressive.

If your manifold leaks down, it's time for a cheap cigar. Light the cigar, take a deep drag (don't inhale though!), and blow that lovely smoke into the intake manifold. Doing this in the dark with a flashlight to find the smoke leaking out works well. Small as the leak was, I saw a tiny bit of smoke coming from the valve in the resonance tube

This also works on the lower end using the oil fill tube, electrical tape, and the corner of a 3 mil trash bag (dipstick tube might work as well, I didn't actually use that).

Best of luck.

I agree but please use a decent cigar. It is a Porsche after all.