98chev.malibu,3.1V6?

every now and then 98chev. Malibu 3.1V6 i will stop at a light, and when i start to go it acts like its not getting no fuel, I've replaced fuelpump, cat converter, 02 sensor, I've put complete fuel and injector cleaner in it, It only happens in the daytime when its hot. Also I can turn it off and let it sit for 20-30 mins. and it goes like nothing ever happen.