i have a 2003 pontiac grand prix gt. i dont have heat . changed thermostat, coolant temp. sensor flushed radator and preasure tested it new radator cap . flushed heater core clean. blower works

I have bleed the system to an temp door is work if I press on the gas in park to about 2 grand to 3 grand. An hole it I have heat until I let off. An then radiator hoses have pressure

Weak waterpump ??

First off there's no such thing as a weak water pump. If its not leaking or squeaking its working fine. While it might possibly be heater core it is extremely unlikely since you've flushed it. What is far more likely is that there's still air trapped in the system in spite of attempting to bleed it. Some modern GM cooling systems are extremely tough to fill properly for some reason. You may want to resort to having a shop do it using proper vacuum equipment designed to pull all the air out as it is being filled. I've also heard that filling it while the car is facing uphill helps although I've not actually tried that. Whatever you do, get the air out of the system and I'm pretty sure all your troubles will be over.