part time running '91 sunbird le?

i replaced EVERYTHING on this thing,fuel,ignition. it starts and runs for the most part. the rest of the time!%*^&@. it looks like it's not getting fuel, stalls & ruff idle. what would make the fuel delivery work sometimes and not others?
car ran good for about 6 months after repairs,and then!@^%
conditions don't seem to matter{hot,cold,just drove,just parked,just yeld at,just kicked,no constant varitable seems to matter. i pulled every senser to check if it's sending signal the ecu is new, everything is new. what ever happened to the basics? fuel,air,spark, and wheels!!!!!go old iron!!!! the fuel pump seems to be the standard anwser. i just want to be sure before i replace MORE parts!
i'm desperate for any insight

rob, March 2006

its fuel comppression and spark
Try checking fuel pressure while you drive it with the pressure gauge on windsheild ...........you will need to find what is missing when problem occurs ......with a scanner attached so you can see what ecm is seeing

bg, March 2006