The Steeda/SCT combo is great. With that buttoned down, I'll talk about exhaust. This is gonna be long, but here we go. I would personally go with all Bassani. I know I currently have Magnaflow axle-backs, but I only got them because Bassani had not made an exhaust yet and I was impatient. I will buy a full Bassani exhaust soon. From what I've seen Bassani's long-tube headers make amazing power; equal to or better than any others.
I have had two previous Mustangs ('01 GT, and '03 Cobra). Both had full Bassani exhaust, and the sound was beyond words. I literally had someone tell me how amazing they sounded every day. By comparison, I've had the Magnaflows (Streets not Competition) on my '11 GT for 6 months now, and I've had only one such compliment. Now, I'm not looking for others' approval, I'm just saying EVERYONE seemed to love the Bassani. Their fit and finish are perfect. I had the exhaust on the '01 GT for 6 years/130k miles with no problems.
One thing about the Bassani, they are loud, but again, everyone loved them. Even older men (and women) who you would expect to NOT like a loud car liked them.
My experience with X vs. H pipes follows. On the '01, I put it all on at once, but the Cobra got the cat back first, then 3 weeks later the x-pipe. The (factory) H pipe was deeper and sounded good, while the X was a little louder, a little higher pitched, and much more burbly. The X sounded more like a Mustang, while the H sounded like a GM LSX motor to me. I like the X better, it will likely make more power too.
As far as cats go, I feel high-flow cats are the only way to go. Just so everyone knows, I live in Alabama where there are no emissions tests. I don't like O/R pipes for two reasons. First, I think they sound bad. I think the cats drown out some of the high-pitched popping. Second, THE SMELL!!! My '01 GT's cats scraped so much that they ended up crushing the catalyst material and shooting it out the tail, so I basically had no cats for a while. Without cats, your exhaust will smell like gas and fumes. It is annoying.
2011 Mustang GT - Kona Blue, 6MT, Brembos, 3.73s, Everything but auto & glass roof.
BMR Springs, K&N Drop-in, Magnaflow Street Axle-backs.
Last edited by Bama5.0; 02-17-2011 at 08:40 PM.