stalls on slow down w/ oscillating idle

[Leslie Brooks]

Good morning all! I bought a 2000 3500 w/ 86,000 miles. Ran great, but always smoked a lot, especially on start up and had some funky idle patterns, no high idle on cold start up and oscillated a bit. Never seemed to have as much power as it should, less than my 93 anyway, and could not go over 55 mph without sounding like it would blow up. I ran all the cleaning agents and replaced all of the filters and replaced the injector pump, no change. I then replaced the injectors and the smoking is better, a little more horsepower, and it easily goes 65 or 70, but now it is stalling out when I slow down to stop but easily pop starts again and runs fine as long as I'm on the fuel even a tiny bit. Also now when idling, it oscillates between 600 and 850, much worse than before. I have installed an aftermarket exhaust brake and the problem seems much worse when I have the air conditioning and the exhaust brake on, these 2 used to be able to run together w/ no problems. Yesterday, I pulled the engine control fuses in the effort of resetting and it didn't help for long. Any help is greatly appreciated. Thanks!