Rough startup after sitting

If my truck sits for more than a day, it sounds like it starts on one cylinder after giving it plenty of fuel and turning the motor over for a few seconds, it shakes for about 5 seconds and it runs fine. Starts fine after sitting for an hour or two. Feels like the injector lines are mostly empty after taking them off and having to re-prime them, but they stay on.



I have swapped the injectors, nothing changed. Put a FASS100 on, nothing changed. When I put the FASS pump on, I ran the injector overflow straight to the tank and removed the stock filter and fuel heater. Has anyone had this problem or know how to fix it?



Thanks.