i have a 93 wrx and all has been well until this afternoon. when stopping earlier the revs died and the car stalled, started straight away but when i let off the accellerator the revs drop to about 400 before going back and staying at approx 900. there is no hesitation an revs. i have opened the bonnet and can hear a whistling near the back of the engine bay, don't know if its related. any help would be good.

 

sounds to me mate that 1 of the boost pipes has come off or split

 

also check your idle control valve. its located near bottom right handside of your intercooler. you can take this off and clean it. this can cause allot of idling issues