[Nazgul280]

Hi Kurt,

I'm not an expert but I can tell you are on the right path with air leaks. If I can relate to a story of mine, it may help you think of other things to check systematically.

I restored an old Z car of mine and had idle problems with the new engine that had so many mods it was unrecognizable from stock. My first startup it raced directly to 4500 rpm and stayed there until I killed the ignition about 4 seconds later. I had numerous leaks all through the custom intake and injector bosses that all added up to an uncontrolled idle.

I've had friends (in non-Pcars) that had vacuum leaks in the climate control heater cocks that caused similar problems. Now who would look for a vacuum leak under the dash?

My point is this: you have already identified at least two potential leak sources. Check those first until you can rest assured that you have ruled them out. Next, go to the more improbable. I would say ANY air line coming from the intake manifold, a Head gasket leak, exhaust gasket are a few more ideas. What does your vintage 911 use vacuum for? Find out and start checking.

A couple of tricks to track down leaks: Simple propane like a Burns-O-Matic torch can be used around your gaskets to check. Here's how. Start your engine and grab the unlit torch with the propane flowing and run it close to all your valve cover, exhaust, and intake manifolds that you can get to, all the while listening to the engine. If the engine stumbles, you found a place that is sucking the propane into the engine and it doesn't like it as much as your Fuel/air mixture.

Another trick that I never had too much luck with but others have is to take a few feet of vacuum or small diameter fuel hose and use it like a stethoscope. Place one end near your ear and with the other you can probe around and listen for a hissing sound, that is, if you can hear it over the engine!

I'm sure others here can enlighten you with some specific paths for your 911, but the problem is basic: the engine has to be a sealed pump and the only air entering is on purpose.

PS: I know this sounds dumb, but are you sure your Throttlebody is returning to fully closed when you release the pedal?