When you "floor" the gas pedal, the ECM goes into a preset fuel-air ratio. Sounds like
maybe O2 sensors, clogging cat or a bad/dirty idle air control valve. If you can get a
scanner tool that reads live data, take note of the O2 sensor and fuel trims. O2 upstream
should move up n down downstream should be steady...just not pegged at 1 or 0. Read
the fuel trims, short and long, at idle/1500/2500 RPM, they should be around "0" when
thew engine is warm and at steady RPM n load. Last, what is the intake air temp reading
in relation to the ambient air temp?