Alright, i have a 1996 nissan 200sx that has never given me any engine trouble until now. The car trouble started out as overheating, which i quickly discovered to be the thermostat. It ran fine for about a day, then it started throwing 4 differnt codes, one was a coolant temp. sensor, tested it was bad so i replaced it, the second was a knock sensor, tested it it was just loose, 3rd is a maf sensor/circuit, checked it everything was fine, 4th is the IACV/AAC valve. The engine also surges when holding the accelerator steady. I checked the EAG valve and t seemed to be working fine, car smells like its running very lean, which makes me think its either a fuel delivery problem, or a vacuum leak. or possibly both. Anyone have any input for me cause im at a complete loss. Thank you.