Last I checked it is a clean air filter. The problem started at the end of last fall when I was still driving the truck a lot. It actually happened when I was driving North to put the truck in Maine. I was on the highway and then their was just a major loss of power and I could see billows of smoke behind me. It wouldn't go over 30 and I had to call AAA to tow it the last 100 miles. The truck idles fine, but any throttle and she just goes Blehhhhh and coughs up lots of smoke.
I have a 6.5 turbo setup sitting around, but if anything got a turbo engine, it'd be Fire Truck.