when i accelerate and take foot off gas ,i get backfire sound -or similar to that.its not loud,but noticeable.any ideas of what to check.these cars have backfire valve,but im not sure how that works.car runs strong,just adjusted valves.someone on 912e forum suggested exhaust system gaskets,but im not sure if they were referring to gasket at headers or muffler.any ideas?

Is it back firing or popping from an exhaust leak?

Exhaust leak

well the responses suggest exhaust leak.any suggestions as to how to find it?

more of a popping sound,can i continue to drive it until i find leak or can i burn a valve etc

take a look at all of the connection points/gaskets - then look at the muffler itself for any holes, especially if you see seams and welds

hope this helps

brad

Look for carbon blowout - any darkened areas around gaskets and such.

Yup... exhaust leak.

If you have a two nipple vacuum advance, check that it is good. One of them helps pull back on deceleration.

Or you already have a burned valve (or not seating properly). The exact symptom I had years ago on my 914 2.0. When I pulled it apart there was a burned valve ...

Check the exhaust leaks first obviously since that's external. You'll hear different methods for doing this, but my favorite is probing around with a length of fuel hose (or other similar sized hose), one end near (but not too near!) your ear, and the other probing around where you think there may be leaks. You'll hear a very audible poofing sound through the hose when you get near a leak.

Scott

noise had gotten louder after adjusting valves.they were definitely tight.im hoping for exhaust leak.heads were recently doen.i dont want to think about burned valve.

would a bad deceleration valve cause this problem?