I have A 1992 929 w/130,000 miles. just replaced timming belt, water pump, pcv valve, dist. cap & rotor, and plugs& wires,and air filter. It ran beautiful for a couple of weaks. My wifes car (93 sat. sl2) was getting realy crapy gas mileage, so I put some of that sea foam stuff in her fuel&oil. worked wonderful gets at least 50 miles more per tank. So I decided to do the same in the 929. After that every time I do a cold startup it has a realy bad miss. there are no vacumme leaks the timming is right on. I even changed out the feul. Once the car has run for 5-10 minnuets the miss is compleatly gone for the rest of the day.. ANY HELP WILL BE GREATLY WELCOME.........