Here we go again... 6nz problems

Hi everyone. Well, I managed to go a little while without having to seek advice, but it would appear that the gremails in my engine have been quietly plotting against me...
I now have about 50,000 miles on my platinum overhaul, and I'm starting to get enough blowby that I saw it in the headlights of cars behind me going down the road tonight. Got to my destination, lifted the hood, and a the tube had I steady supply of smoke coming out of it. I pulled the oil fill cap and it started blowing out of there. I have noticed my fuel mileage go down slightly, also when I'm putting the fuel to it I can feel a "thump" on the floorboards and pedals. The best way I can describe it is it feels like a tire has a flat spot, but it's too fast and changes with rpm and throttle input. I can barely feel it when parked. Could it be that I just need to run the overheads? It doesn't seem to be using any oil. No smoke out of the stacks unless I stand on it, then it's just black smoke. As always, I appreciate all the help I can get!

 

Yeah, it's only been 53,000 and some change since it's been rebuilt. If it's a piston problem caterpillar is going to have to eat the repairs hopefully.

 

No, I kept the turbo that was on it. It isn't using any oil, and I am going to get another oil analysis done at my next service.

 

The air compressor is new, also. I put it on just before I did the rebuild. Would it pressurize the crankcase enough to cause blowby out of the oil fill?