I just traded my 01 2500 off for a 96 3500 the 96 has a modded fuel plate and 4 inch exhaust. The truck runs good and strong.but when sittin in park when i rev it up it smokes black and then is followed by a small puff of white. What could that be.the guy i got it from said he modded the plate his self by making the holes bigger that the screws go in. And it lets it slide more. But when i rev it it revs quick but sounds to miss very very little. But when i hold the brake and spool the turbo it only smokes black any ideas

 

That's the first time I've heard of enlarging the holes, don't think it would work.
Most people grind the face of the plate instead.
Try moving the plate towards the rear about 1/4"

 

I'd start with (in addition to above post) simple things like fuel filter, fuel heater pre-screen, and fuel pressure check. My truck did that when I neglected the heck out of it and didn't change fuel filter for....long enough to make the filter look like a big snot. Now it does stumble a bit when revving with no load and cold, also starts a bit rough in the cold sometimes (always had) so I'm sure I have a fuel system leak somewhere.

 

i bought a fuel filter but its got a spot on the bottom to screw something in to it on the bottom but i dont see anything on the one on my truck any ideas

 

Thats the water drain. Sounds like he put one on that didn't have a water seperator. There is a valve that screws into the filter that will let you drain off the water. Call him and ask him if he's still got it. Otherwise buy the same filter he has on there.

 

White smoke under no-load sounds like retarded timing to me. I agree with infidel, never heard of modding the plate that way.