So far I just installed Flowmasters 40 series with some chrome cat tips that are pretty wide and I like how it sounds. I already have a CAI in there and want to put more to make it louder and bump up the HP. What else can I add to it? I was thinking a BBK 56mm throttle body for now but what else? I have a 1998 Mustang V6 3.8L. Thanks all.

 

The 56mm won't do squat unless you port match the upper intake to the size of the TB. Even then the hp gains will be minimal. Get gears and a differential, or a 75lb shot of N2O. If you're gonna get a TB, then you might as well get all of the supporting mods, like a ported upper and lower intake, cam, and heads. But if you're gonna go that far you might as well do a split port swap. Cost about the same, and you'll get way more hp. You will need 19lb injectors though, and a MAF set to them, I say get 24lb injectors and a 90mm MAF set to them. You won't use that much fuel, but if you do decide to use a shot of N2O, you'll probably need them.