oh ya and a gas and oil mixture leaks into the airbox but all crankcase ventilation components are clean and in good shape
I've replaced both in-tank and in-line fuel pumps, cleaned the idle stabilizer and throttle body, changed the air filter and spark plugs and wires and checked all of the vaccume hoses for leaks and clogs. and I have ran the car on premium fuel with injector cleaner. The car still sputters and hiccups, when first started it runs fine for a bit but after around 30 seconds the rpms start to go down and the engine sputters around, and when i push the gas the engine stalls a bit and the rpms go down and it backfires in the airbox, after pumping the gas i can get the rpms up enough to drive it, i'm completely stumped. any ideas?