1989 Ford Taurus Idle?

I have a 1989 Ford Taurus GL with a 3.0L Vulcan V6. When my car is cold, and I rev it, maybe 30 seconds after it been started, when the RPM's come down, they go down too low, and it sputters, the goes back up to normal idle. It also does the same thing when I go into reverse, and it kinda does it when I go into drive, but for the most part, reverse. When I have it in park. I always backout of my drive way, then put it into drive and drive off. Well at a stop sign not to far away from my house, I decided to put it into reverse, since it had been clunking into reverse, and I wanted to see if it was still doing it. So I put it into Park, waited about 5 Seconds, then put it into reverse, and the RPMS's dropped, headlights, and interior lights dimmed, then the idle went back up to normal. I have done a tune up myself on it about 3 months ago. I changed the sparkplugs to Platnium ones, that last 75'000 miles. I changed the rotor in the distributor, and the fuel filter, and put in Lucas Fuel injector cleaner, and also ran my car on this stuff from a can, it wasnt seafoam, what it was was a can that hooked up to the fuel injectors, and we byped the fuel system, turned it off, then ran the car on the can, until it ran out. Ran reppt good after that. Then about a month later my car started idleing weird, it would rev up and down quickly when it was cold., maybe 250 rpm difference, and it would be maybe 1150 for half a second, then drop to 900, and continued to do that, at an idle. I noticed that it stopped when it was warmed up. about a month ago I disconnected the battery for a minute and hooked it back up and it problem was solved. But now its starting to do that thing when I put it into gear when its cold, but the RPM's dont hunt around like they did before I disconnected, and reconnected the battery. Whats wrong? I also used a m airflow sensor cleaner on it when i tuned it up about 3 months ago, since the oil from the KNN filter got on the sensor i guess.