I would suggest getting a chip or tuner. I have been doing some research lately as I am looking to get one myself, and I think I've found that the best bang for your buck would be the SCT Mustang 4-bank eliminator chip. >>>
SCT Mustang Performance Chips at AmericanMuscle.com - Free Shipping!. It is under $300 and from the reviews I have read, it gets the job done. I also read a random review a couple weeks ago saying that when they got there car tuned it made the car sound better also (aka utilized the aftermarket exhaust system better). I'm not sure how true that last part is, but just something to think about. Good luck!
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2004 V6 3.9L Mustang (automatic)
Go: Fenderwell Cold Air Intake, Dual Exhaust (no crossover) featuring a MAC catback, SCT Mustang 4-bank eliminator chip (tunes by Justin @ vmptuning)
Show: Stainless Steel Bumper Insert Letters, 8" Chrome Shorty Antenna, Mustang License Plate Frame
God bless all!
