2004 grand prix stalling

I have a 2004 grand prix 3.8 engine that keeps stalling. I notice it happens mostly when speed up and go up hill. I changed the crankshaft sensor and cleaned the throttle body. But didn’t help. There’s no check engine light on. Any ideas on what it can be? Thanks.

Also did a fuel pressure test and it was fine.

Good fuel pressure does not necessarily equal good flow. What’s the fuel pressure when the problem’s occurring? Check for plugged cat. My specs say “less than 1 psi @ 2000 RPM in park”.