[Jhalsey]

My 1989 930 which has under 50k miles and is stock other than a CAT bypass pipe and a Permatune CDI box, stumbles under acceleration until around 4000 rpms when it clears and pulls. Seems to be happening more frequently. I drive it every two weeks, maybe 20 miles round trip. Motor and turbo were rebuilt 7 years ago. Other than this stumbling problem, runs great, excellent acceleration, good idle (does go to high idle when restarted when warm but it is my understanding this is normal until the ICV gradually bleeds off rpms to reach normal idle speed). Appreciate any suggestions on how to go about trouble shooting the problem.