Hello, I have 1991 Mazda B2200 w/ 120k miles. Runs perfect until it spudders, with raw gas smell from exhaust then stalls. Hot, cold, doesn't matter. Wait a while, then it runs perfect again. Always has spark and 37psi fuel, and DC pulses to injectors. Throttle position sensor checked good with ohm meter. No codes from ECU. ECU looks perfect (no leaking electrolytic caps). Any ideas?