Unstable Idle soon after starting and with a cut off sometimes

Engine unstable soon after starting and misfiring when raved beyond 2000 when stationary
Fuel pump shut off switch is in pressed down state all the time, no fuel from the return pipe going to the tank.
The air bag signal flashing for sometime
after vehicle runs for about ten minutes engine stabilizes but with irregular idle, when you press accelerator peddle down with a kick it produces a pink sound like engine about to cut off
In short it is like engine is running with choke on

Please advise