When de-acceling car sputters.

[EclipticalGS]

Car has been idling worse and worse and can't figure out why. Anyway, this just started not to long ago , but when i get on the gas a and get into the higher R's my pulleys will sound like a turbo spool no joke its louder than my 3" exhaust. Any also...now when say im ni second gear coming up to a stop ill let off the gas and let the motor kind of slow me down, and ill hear sphtuhpsphut like a fast sputter. Does this mean i have an exhaust leak..because my braided metal looking resonator or w.e has wear marks from being constantly hit ### the car is so low. But theres not a hole in it. Also i have new plugs and wires Ngk iridiums gapped perfect etc.