I had a Raider (2.6) that dieseled like you descibe. I got used to hitting the a/c just as I shut it off so the compressor would drag it down. Not much help, huh?
Don't adjust any of the screws just yet. One of them says in the manual not to adjust, as I recall (which is why it has a philips head on it and is accessible?).
You might be surprised at how it does in emissions. You might not, too. I've had my share of trials and tribulations with IM-240 here with my Monteros. If you flunk it, scan the trace that you can pull down off their website when you get home and post it up here.
Have you thought of water fogging the running engine to burn off some more carbon? Also, take it out on the freeway and hold it at the speed limit for as long as traffic allows, like a half-hour. Get it running hard for a while. And nothing's harder for a 2.6 to do than pushing that refrigerator box through the wind for a long time.
AC button! Good idea! I'l give it a shot, John! Thanks!
No touchie the carby until I've got qualified counsel on-hand to guide me, imo. Looking into the void with the air filter off while I was 'foaming it, I noticed there were two "barrels" (I guess that's what they're called). The one closest to the driver's side has a sort of hexagonal flapper in it which did not appear to so much as flinch, even as I gunned the throttle by hand. It was too dark to really tinker, but I'm still too green to know if it's running strong or not at this point. She'll do 70-75 on the 101 around Phoenix, and I can be pushing 50 at the top of 3rd gear, but I'll be damned if it doesn't sound like it's just making more noise.
Whatever the results of the emissions test tomorrow, I'll post up here. Appreciate the continued advice.