01 p71 shaking at cruising speed

I have an 01 p71 that is about to drive me nuts! I bought that car from a police auction. The plastic intake was cracked tr the heater hose boss ,so i jb welded it and poured in a thang of dike. That fixed that problem. My problem is after you get up to speed and start cruising it starts to shake. You can excellerate and drop a gear and it goes away. I have put in a new cop on nuber 4, put all new boots and spring, new motercraft planum plugs, cleaned the maf sensor, put in a bottle of lucus injecter cleaner, swapped the o2 sensor around ( once it gave me a code for bank 1 sensor 2 so i cleared the code and swaped sides to check them) no code has ever came back up, put on a new battery, i even gutter the cats today to see it that was it. I took a co out of my truck and tried it on every cylinder still shaked when it goes into over drive. I changed the trans filter to day and drained the tv also. It still does it. I'm at whitts end! Plese help me someone!!!!
I was wondering if it could be the fuel fiter? Seem like it would do it under a load if that was the problem, not cruising.

I had the same problem i think , sounds the same . Kinda shakes or bucks while in overdrive at a steady speed and goes away when you increase or decrease the throttle. try disconnecting the egr vacuum line and plug up . Take for a test drive if problem is the same then egr is good.Replacing the egr fixed my problem .