> Seems like a vacuum leak would show up all of the time, this problem comes and goes.
I'm an old fart, and I've found that the more you define the problem, the more you define the solution.
You could have a small leak, that shows up more often at times of more vacuum. There's been a lot of postings of rough idling and the engine acting up when coasting down a hill- all symptoms of a vacuum leak at high vacuum situations. When you step on the pedal you get more air ~ less vacuum. If the air/fuel ratio isn't right you may be getting an occasional misfire.
Then again, there could be other causes. Dirty injectors, a small head gasket or manifold leak, a bad O2 sensor, a misadjusted TPS, a loose spark plug wire or a misfiring spark plug. And many times it's more than one thing.
> I'll try the clean up.
Do the easy/ cheap/ free stuff first. Then check the next level of potential problems and parts. At least you can cross them off the list.