I recently had my fuel pump replaced. But still having starting issues when cold

What is your question?

I recently had my fuel pump replaced. Would run fine for a while then same issue. 4 fuel pumps later having same issue. (Warranty) Battery also replaced last time failed as they thought low amps. Still same issue. I disconnected battery then hooked back up and it started this time. Before I could spray starting fluid and would start but not this time. Any clues as to what else could be? Computer maybe? Edit. Took back to repair shop and replaced regulator valve. Pressure drops rapidly when sitting. Read elsewhere it could be injectors? Repair shop And I are at my whits end

What makes this problem better or worse?

Starts when warm

How long has your 2001 Chevrolet Express 3500 had this problem?

Early November 2018