i have a recently revived 91 3.0 LWB that i got an emission waiver sticker for this year in PA, ...it idles high all the time, never gets below about 1200 rpm. the local chain shop couldn't figure out how to adjust it...plus the exhuast emissions are noxious, and will make me sick if i drive it for extended periods of time. not black or white or blue or anything, just smell bad and produce headaches. engine otherwise runs well and smooth, does everything it should, still getting halfway decent mpg, etc... tips? are the two problems related?

You shouldn't be getting fumes in the rig just driving around unless you're also doing a lot of just sitting around.

If you are driving and getting fumes in the rig, you likely have an exhaust leak or the tail pipe's been cut too short or you have a hole somewhere in your floor.

As for the high idle, I'm sure someone else might have insight on that.

it's become noticeable in the warmer weather, driving with the windows down. the exhaust has always been really noxious since i got it on the road--but not really an issue once in the truck. if i have the truck running in the driveway, anyone who's within 30 feet gets the bad fumes.

exhaust leak and a bad iac motor

I have chronic high idle problem that comes and goes.

Ist you need to hook an analog ohm meter to the data conector and see if you get any codes.
The 2nd fix is to put the right thermostat in. It must be 195o for the temp sensor that talks to the ECU so the ECU knows what the engine is doing.
A bad O2 sensor could make it run rich,,,but not as rich as your discribing.
The ICS could be bad ,,,and this does not give a trouble code to the ECU, so it has to be removed and tested.
Mass air flow sensor or the TPS/idle switch could be bad. These will give codes.
You could have an extra sensitive sniffer , which is a good thing,,,after I went thru chemo any toxic fumes get to me. A good sniffer is the normal natural state for us before the industral revolution desensitised most of us.

Do you think the cat is getting clogged? I "deleted" that option & mine runs great. No noticeable fumes!(I know some of you west coast guys' skin is crawling about now !)

i'm not a mechanical expert, so not entirely sure what all those abbreviations are, haha. boy i feel stupid.

i will have it checked for a leak--but again, the smell of the exhaust outright is much worse than any vehicle i've ever owned--and i've owned several with some bad exhaust leaks. drove it into the office this morning--felt vibrant and alive when i got into it, and after a 20 minute drive, i have a headache and feel sick to my stomach.

based on what was just said, not sure if this plays into things: previous owner bypassed the fuel relay on the ecm and it simply has an under-dash fuel kill switch.

all that said, what exactly is it that gets adjusted or replaced when the idle runs that high (it doesn't really vary. it's right around 1200 from when it starts and never changes much.

ECU = engine contoll unit, the brain for the fuel injection/emmisions system.
ICS= idle control servo, a little motor on the Throttle Body that contolls an air passage used during warm up.
TPS/idle switch+ tell the ECU what position the butterfly in the T.B. is in. Also is a kind off on off switch for the idle position.
I can't imagine why somebody would bypass the MPI relay.
That's not good. Many 3.0 and 2.4 mitsu manufactured vehicles use a compatable relay that could be gotten at the junk yard pretty cheaply.

here's another thought on the rich fumes,,,,
possibly a cracked diaphram in the fuel pressure regulator. That would allow gas to be sucked into the plenum.
Pull the vacuum hose to the F.P.Reg off on the back side of the plenum and see if these's gas or strong fumes.
The F.P.R. sits between the plenum and the firewall near the trottle body.