I don't think it's using oil. I've never noticed, and it only has circa 80k
on the motor. But, I'm due for a oil change, so I'll be sure to check
carefully.

I checked the plugs today - These are new plugs, about 350 miles old -- and
they're starting to get the black goo on them that raised my concern two
weeks ago. The fouling is uniform across all spark plugs.

I  pulled codes the old fashioned way (CEL) and I think (did I blink or did
the light?) I'm getting an IAC code.  I pulled the IAC off, and it looks
clean. I shot some carb cleaner at it, but I might replace it anyway. As far
as I know it's the original.

As it stands now, I haven't had any hesitation problems - probably due to
the new plugs - but it backfires and idles a bit high and rough. The
backfires are at startup and sound close to the engine. It's a series of
quiet bumps rather than pops. At idle it'll  subtly backfire every 5 seconds
or so, the idle will go to about 1400 and it'll run okay. Then, when it
drops back to sub-1000, the backfires will return.  If I turn it off then
start it up again quickly, the backfires will be much worse for a few
seconds, then return to the every 5 seconds rate.

The only thing I've done to the car -- pre hesitation/backfire problem --
was to change from an off-road H-pipe to the cat equipped X-pipe. I put all
the EGR/Thermactor stuff back on in the swap. Post problem I put in new
spark plugs, cleaned the IAC, O2 sensors, MAF and adjusted the fuel
pressure.

Other than the IAC I'm at a loss as to finding a solution.

Jim S.
'82 Mutant - 93 5 liter