So I have a 2006 5.9 Cummins. I’m having a hard start and a surge when going down the highway. When it’s a cold start the truck will start and die within a second. Then the next attemp it starts, sputters and almost dies but catches up and idles normal. I hooked up the scan tool and read that I was only getting 3000psi of fuel pressure at first start up. My set point fuel pressure when the truck is off is 2500psi and when it’s running it’s 7000psi. But if i drive the truck to the store, shut off and come back out 30 minutes later it starts just fine. Also when I’m driving down the highway between 65-85 I get a huge surge in fuel pressure, roughly a 3kpsi spike, and the truck kinda shakes. I thought at first it was possible my TC locking and unlocking but my snap on says otherwise.

Here’s the mods I have.
Fass 165 with sump
Dual CP3s. Stock bottom and LBZ top
88% over II injectors (full body)
Diesel power source twin turbos 362/s480
Fire ring head
103# valve springs
Extreme duty pushrods
Built BD 48re
Efi Live by maverick diesel

Here’s what I’ve done for troubleshooting
Pulled the injectors and had them tested. They came back good. Went thru and retorqued everything in the fuel system to include connector tubes, fuel lines and hoses. Replaced the stock cp3 with new. Had LBZ cp3 rested and it’s good. I have no fuel leaks. Possible air getting into the system? Any input would be great. I have 15psi from my fass at idle and it goes down to about 6psi at WOT. Possibly bad connector tubes?