I'm getting exhaust this weekend but don't know about the h-pipe or x-pipe. is it worth getting it and what will it do for me. I'm running a 454 with a 580 lift cam and 3000 stall with th 400. thanks dave

I think the x-pipe will give you more hp. I have the h pipe on my car. The x came out a few years later so i did not have an option.

I have the H pipe flow master header pipes, if the X would have been available, I would have gotten it. If I get into this area again , I will change.

how much hp and is it worth it. I just want my car done right . don't want to redo anything twice

How much increase do you want?

You won't see a huge increase in horsepower from the X, but it will be there. The additional benefit of the X is it will quiet down or "smooth out" the sound, I really like mine. I've had an X on my Mustang for 10 years now I think (w/ flowmasters), and just switched to an X a year or so ago on my Camaro (magnaflows), I definitely like the sound much better and while the Camaro was a complete change the Mustang was a direct H for X swap, and I felt a small seat of the pants increase for sure, particularly off idle and WOT response.
I also wouldn't consider anything but a Dr. gas X, they are a bit more money, but I have never seen any other X that was as well built, I have two and one has a ton of miles and 10 years service, and it looks like it did when new.
Difinitely another vote for the X :thumbsup: