2003 monte carlo hard to start warm engine

My 2003 Monte Carlo 3.8 SS starts fine when it is a cold start, but if I drive it and it warms up, sometimes it starts and other times it acts like it is going to start and then shuts down. I t takes as many as 4 - 5 times to finally get it to start. It has been in the Chevy garage. They cleaned the fuel injectors the first time, second time they put a fuel pressure guage on to monitor. They haven't replaced any parts yet and the problem still exists. Any ideas.. as this is frustrating

it's still under waranty keep bugging them until it's fixed. might be a bad sensor or a glitch in the computer program. it's your dealers job to do whatever it takes to make you happy since you paid for the waranty

They replaced the fuel pressure regulator on the car to correct the problem. So far so good. Any thoughts on this being the solution?

I have a different problem. My 02 idles rough when I start a warm engine. I primarily use 94 Octane in it and occasionally put in an octane booster once a month.

The fuel pressure regulator worked for a week and a half to solve the problem, then it was the same problem as originally posted. It went in the garage again and they replaced the throttle sensor(TPS????). It has been fine for the past 6 days

Most of the 3.8's had fuel pressure regulators that leaked. So much so that gm replaced many on the H-bodies under recall.
These motors have a unique start program that fires all the injectors at once, then watches for the cam sensor signal for correct firing sequence. This can cause some interesting things when cranking like phantom starts, popping and hissing. GM is aware of the possibilities and are dragging their heels on a good fix.