Stallin and a Smokin

OK, My jeep is a 92 laredo with 3 inch lift and 31x10.5's. The motor (4.0 H.O) has 215,000 and runs fairly strong. The other day my buddy was driving behind me and said he could see black smoke come out of my tail pipe when the jeep was shifting. Why is that and is there anything i can do about it? I also have been stalling right after starting motor and after it has been sitting for a while as soon as i put it into gear. I have cleaned out my idle stepper motor several times using a can of carb cleaner but have never taken it off and cleaned it. After i spray inside there with carb cleaner it runs better for a month or so then goes right back to stalling. any ideas? sorry for all the length of this post! Thanks!

i had this problem (it sounds similar at least) and i had a bad throtle position sensor. is the CE light on?

its something to try...

clean the throttle body and try cleaning the tps.

If it were the tps you would have revs and you would be stalling all the time and have a really rough idle.

I will probally need to have a new tps sensor put in. Does it need to be installed by the dealer? But I dont think this is why i am blowing black smoke. I cant see the smoke in my rearview mirror but i was just wondering if there was anything i could do about or just forget about it. Thanks!