90 Chevy 3.1 has a dead spot on acceleration?

fuel pump fuel pressure regulator and check the coils :{

first, after warm shut down what is rest fuel pressure? it should be at least 20 psi after 30 min. if not block off pressure and return lines[do not pinch plastic tubing fuel lines , if equipped] if pressure still drops check for another leaky injector[s] or fuel press regulator leak through vacuum port if all ok here then check fuel press running [should be approx 35 psi with vacuum to regulator] if not replace regulator.

second what do the temp sensors say? [scan tool state display] or ohm meter reading coolant temp sensor at operating temp[180-195 deg-f] should be approx 200-290 ohms. air temp at 65-70 deg. f. should be 2000-3000 ohms replace as required

third these early engines used both a air mass sensor and a map sensor, both gave trouble map sensor was usually hidden near pass side firewall [follow vac hoses] and was the least prone to give trouble. the air mass unit the most prone,[the mass air sensors always tested good] but car would never run or start properly until replaced. good luck and no smoking or bare drop-lights around fuel and or open fuel lines..

Try the coolant temperature sensor. If it is not working, the car thinks it's cold when it's actually warm, and supplies more fuel, flooding the engine.

i had alumina with that problem, it turned out to be a bad fuel pump, also vapor lock in the gas tank, try loosening your fuel cap that mayhelp. any other questions let me know, i am a certified auto technician, also fuel pressure regulator, another problem those are know for id the coil packs, and also ignition module.

Have you checked the fuel pressure regulator?

sounds liek to much fuel pressure to mee

sounds like lifters