The archives have been helpful in pointing me in the right direction, but I
though I'd ask about my specific symptoms ('90 2.1L):

Rough idle (occasionally will barely stay running when cold)
Hesitation/loss of power/bogging under acceleration (sometimes need to back
way off on the throttle to accelerate w/ out bogging)

It used to be that when the van was cold, it would always start, accelerate,
and drive fine.  Then, after, say, a 30 min fwy commute, I would come to a
stop and notice the rough idle and poor acceleration.  But now, it happens
even when cold.

It always cruises fine (or at least the symptoms aren't noticeable at
speed).  I'm aware of the "intermittent syndrome," but from the description,
it seems like this problem usually causes sudden power loss while cruising,
and can be temporarily cured by turning the car off.  Not so w/ my van.

This problem seems to recur/disappear in long intervals.  That is, it will
run fine for perhaps several weeks, than misbehave for several, with only a
few occasions in between that oppose the trend.

What would be the most likely problems and how can I test?

Thanks,

James
90 Carat