1999 OLdsmobile Bravada Service engine

1999 OLdsmobile Bravada Service engine light came on and went off. 2 codes po300 and po152. sluggish acceleration. sounds the the vehicle is starting out in third gear or overdrive... very low pitch noise to engine. when you step on the gas pedal as though to pass someone the rpm increases but the speed is gradual. fuel pump was replaced/filter for lack of fuel pressure. another code had been set for the O2 sensor located between the muffler and the cat converter. This is a completely rebuilt engine from Jasper with only about 17K-18K miles. The air cond. also doesn't switch to just outside air with air off...like vacuum switch/line problem??? the flasher noise is also sounding even when the turn signal is not engaged and the sound is stopped by pressing and holding the emergency flasher button down several times