I have an '87 carbed 22r. I'm having a few problems, maybe unrelated, maybe not:

1) Engine seems to run fine, for the most part. Starts at zero degree temps no problem, after pumping the gas a few times. The cold (fast?) idle starts off at about 1200 rpm, and as the engine warms up, it gradually increases to about 1900 rpm, until it kicks down to about 800 when it's fully warmed up (after a few minutes idling). Any ideas for the gradual increase in idle?

2) Once the engine is warm, it usually is somewhat low on power, until I rev it over ~3700 rpm. At that point, there is a surge in power, and suddenly it pulls a lot better. From there on out, it drives fine. Some days though, the "surge" never happens, and I can barely get over 60 mph on flat ground. Vacuum advance not working right maybe? The carb is pretty damn clean; I had it off a few months ago and there wasn't any buildup anywhere, and everything seemed to work nice and smooth. I don't have a timing light to check if the vacuum advance is working, unfortunately. Any other ideas?

3) Recently, there have been a couple times when I've shut the engine off, and the engine will run on for a few seconds. I've heard of this happening when there is a lot of carbon buildup on the pistons, and with the carbon heated up the engine basically diesels. But, I seafoamed my engine a few months ago and I got NO smoke at all (poured 1/3 bottle directly into carb with engine running). So, I don't think I have any carbon buildup. Any ideas for why it would run-on like this?

Thanks.