[Jamie '92 968]

Trying to describe this thing is not easy. This "shudder" could be a misfire/stumble.

I hope you are right Rick. I am about 10k overdue for the fuel filter, and have one in transit from Pelican that should be here the day after tomorrow.

Still seems like a strange coincidence that this thing showed up on the way home from service where the timing belt was removed/reinstalled (lower balance shaft cover seal). I also had the valve cover seal replaced. Any chance there could be something out of place or loose that the tech would have disconnected during these jobs? I also had a heater valve replaced and a high pressure steering line. My car has a lot of leaks...

I was experimenting on the way home from work yesterday. I could pretty reliably reproduce the problem if I pushed the gas pedal more than about 3/4 to the floor when the RPMs were between 2000 and 2500. If it was 3000 RPM or above, it wouldn't happen. This seemed to work in any gear, though I mostly experimented in 4th, 5th, and 6th. Not sure if this would tend to invalidate the fuel filter/pump theory.

Even if we don't get a conclusive answer until next week when I go to see Pete, I really appreciate all the info. I'm learning a lot!