Sticky Lifter?

Thanks for all the advice, suggestions, etc. Drove the car again yesterday after checking the oil and the noisy valvetrain was back, but this time it just didn't want to go away.

I've heard both good and bad things about Seafoam but I thought that the rewards outweighed the risks in this case so I dumped a third of a can of it in the oil. Let the car idle for five minutes and then hit the road. Drove about fifteen miles on the highway and everything seemed fine. Got off the highway and turned onto my street where I got on it up to 5000 rpm. As soon as I lifted the gas pedal, the noise was back with a vengeance! I immediately pulled over and the engine was idling very poorly, there was definitely a cylinder misfiring and the whole car was shaking. Shut the engine down and let it rest for a while. When I started it back up I planned on just limping the 100ft to my garage at little more than an idle. I drove it very gently for a couple of seconds and the noise went away and everything was fine again.

Hooked up the vacuum gauge and did a couple of tests today, couldn't detect any problems at all. Good, steady vacuum in park and in drive. Took a short test drive and all was good. Seems to be OK for now, maybe the Seafoam finally cleaned up whatever needed un-stuck. I don't know, I'll probably end up having to replace all the lifters sooner than later, but for now it seems fine.