Please help me!!!

My car is driving me insane! Sometimes it drives perfectly fine. Then out of nowhere it just starts hesitating. You can be driving and put the pedal flat and it just revs up and down and backfires something fearce. Usually if you pop it out of gear and restart it, it will run just fine. It will press your back to the seat. It has new main pump, filter, plugs, cap and rotor, wires, and air intake hoses. The best way to induce the engine to do this is to wait until it is completly cold. Then turn it on and let it idle for about 15-20 minutes. The hesitation is so bad that you might as well not even drive it. But if you turn it off and back on it is perfectly fine. Could I be looking at a bad throttle switch or ignition control?? Heeeeeeeeeeeeeeeeelp!

I have had, on my very first 90 Volvo760ti,the exact same problem. Forgive the laymans terms I'll be using.By the passengers left knee there is a panel that comes off and there are several boxy looking things there.I think they are mostly relays. If memory serves me correctly "B" was the one that solved my/your problem. I bought one, around $60,I think it was some sort of fuel relay. There is a woman Volvo shop owner in Tall, Fl that can usually diagnose most fuel things on the phone. Don't know the number right off hand, Vol-Tech is the name of shop. Been turning Volvo wrenches, learned from her dad, for probably 30 plus years.