2006 peterbilt 379 cat c15 mxs on going fuel issue

First time posting hoping to get help with my acert I have been having an on going issue with power loss and smoke coming out of the stacks (blueish white) I have changed all fuel lines from tanks( did that in Hope's to help a fuel leveling issue), new fuel pump, have changed filters (that fixed the problem for 1k miles then back to the same sputtering and smoking first it was at 1400 rpm and higher now it's when I shift and the rpms drop it sputters I have had it on the computer 1st time nothing came up no check engine light 2nd time low fuel pressure new filter and problem solved for about 1k miles I have also changed out the splitter valves that are on top of the transmission from tanks to filter not sure what else to look at theres no check engine light and getting tired of throwing money at things that dont fix my issue any help is appreciated

 

Last time in the shop which was 3 weeks ago I had a cut out test and found issue with fuel pressure replaced a fuel filter and power came back and no smoke also had an overhead ran when it was down runs great after about 1400rpm feels like I have all my power just smoking a little and sputtering before hand also feel like the fuel mileage is down also

 

I'll let you know as soon as we get some down time trying to finish up the harvest here will be testing later this week

 

Had to put it in the shop they did a road test and narrowed it down to cylinder #2 now waiting on the answer if its injector, valve train, or cam hopefully it's the cheapest