Fuel pressure fluctuates
 

I have a 98.5 auto that I did a 5 speed swap on. It has a fass titanium lift pump. My fuel pressure fluctuates intermittently about 10psi while cruising and sometimes at idle. Lift pump also will not run for the 25 seconds after bumping the starter. It runs consistently once the truck starts. Never any starting issues. When I command the lift pump on with a scanner it runs for 2 seconds then off for 2 seconds, then off and does that continuously. Could this be an ecm going out or a programming issue after the 5 speed swap?