Take off the air silencer and install a K&N air filter. It helped mine come down out of the rpm's faster, like when you sit there and rev the engine, for example. It'll breathe alot better. IT DOES MAKE A DIFFERENCE (air silencer removal). Just speakin' from experience. The stock MAF is already 80 mm, plenty big enough, though you can cut out the post that's in the center of it. I believe that on
www.mustangworld.com they have a tech article on how to exactly do it. You must be very careful, though. Get an off-road H-pipe at least. Your 6 cats are making a huge restriction on the exhaust flow. NAmotorsports has MAC off road H-pipes for around $109. I'm doing that and leaving the stock mufflers and tailpipes. I've heard them with that arrangement and it sounds awesome. Almost like Flowmaster just with out the real metallic sound. Real deep and throaty sounding. Then, like they said, eventually get the gears (3.73 for daily driver) and underdrive pullies. Those are pretty much the basics for the car. Do suspension mods too. You could also loose some weight (the car). Kind of strip it down a little. Mine's already like that and it does make a difference. I love it. Good luck.
PS: You can make your own ram air later on or now if you want (very easy to do). So don't throw away the silencer if you want a sealed ram air. You can make the ram air and leave the air silencer off. It works on mine.
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1996 Mustang GTS
All stock (not for long)
15.4 @ 94.4 mph (1/4 mi.)