I'm getting a black/gray smoke when I step on it, seems to be getting where I see it more. Before if I stepped on it two or three times it would clear. Now, 5 or 6 times before it clears. truck has 12000 miles on it and the injectors have been checked and I was told they are ok.

Paul

Does the engine start rattling also? If so it may be your fuel pressure regulator. Mine did this with 1500 miles on it but cleared up with a few treatments of stanadyne fuel additive. GB

I had the same problem. Dealer told me that the #5 injector was bad, but told me to run Stanadyne Fuel additive every 3000 miles and it would clear up. I had them replace the injector, and still add Stanadyne every 3000 and have never had any problems.