Once my 91 TBI warms up it sputters/bucks/pops when any load is put on it. History: Truck ran absolutley awesome until approx. 3 weeks ago. On my way home from work my heater core started leaking inside and gave me a "buck" every once in a while. No big deal. Changed out core and while I was at it, changed out 160 deg. therostat plugs and brakes. Went for test drive and it started to sputter when given load. Thought maybe I had bad gas,so in went some dry gas and some Lucas. Over the couple of days it got worse. I then changed out cap/rotor, air cleaner, fuel filter. No help. My friends had me convinced it was a fuel pump, so I changed that. Drives much better, but still sputters under load. Since then I've swapped out EGR valve, checked resistance of coolant sensorand plug wires (good), replaced termostat with new 195deg. and replaced only broken vac line I could find. Used my chilton man. to check voltages at MAP sensor and they are all jacked up, but I fear that it may have an underlying cause. Like I said this only happens when engine warms up, runs great when cold. ANY SUGGESTIONS? HELP IS MUCH APPRECIATED!