Cummins NTC 400 Big Cam 3

[Bullseyetrucks]

I have a Cummins NTC 400 Big Cam 3 that was rebuilt prior to me purchasing the truck. It had roughly 20K on the truck after total rebuild. Crank polished, liners, pistons, heads, push tubes, injectors... The truck smoked a fair bit when starting out but would for the most part clear up like they are supposed to. It gradually began losing power and started smoking more after 15K miles of me having the truck. I had the overhead ran and it seemed to get a little worse. It began smoking considerably more within a few thousand miles. The white smoke quit clearing up and the fuel mileage dropped. It stunk like raw fuel and began making a BAP BAP BAP (sounds like a machine gun) sound when under a hard pull. It seemed to have a popping sound to it as well. I was told it was a bad cam. I had 3 different mechanics look at it and they all had different ideas. I decided to change the cam and see if anything else showed up in the meantime. There was a bent push tube that was discovered in the process of changing the cam. Everything goes back together fine. It rolls out of the garage and the popping sound to the exhaust is gone but otherwise everything is still the same. Same white smoke, same lack of power, same BAP BAP BAP noise under a load, everything is the same with a new cam. Fuel pressure was checked and it sustains up to 240# and the anaroid valve is good. I took the truck to a different mechanic, he says its injectors and that will fix it. The injectors had 300 miles on them but were not "cummins" injectors so the injectors were changed 3 times now in 35K miles and that changed nothing. Between the two trips to a garage, we tried to haul a load with it and the turbo went out of it so that has been replaced as well. Pretty much everything has been replaced and it still runs for crap and can't be used. Do any of the guys on here have any idea what could be wrong with the engine? I did notice that it seems to have a bunch of blow-by now. I have spent thousands on this truck and nobody can seem to figure it out.... Any help would be greatly appreciated.