Sterling302

This isn't a question about which one to get, it's to help me understand so I can make an educated decision in upgrading my exhaust.

To my knowledge, my exhaust works as follows:
Headers --> Midpipe-Cats-Midpipe --> Resonators? --> Mufflers --> Tips

Of course, correct me if I'm wrong, thats why I'm here in the first place!

Basically I have a dilemma and I don't know what it is.
I want to have a better flowing exhaust for my Mustang as I am thinking of going Forced Induction this summer. I am being told Long Tubes everywhere, but hear my plan out first, and then correct me as politely as possible, lol.

I want shorty style headers, high flow cats, an after-cat H pipe, and thats where I think I have a problem. See, I already have Pypes axleback exhaust. I installed it myself, but I noticed that if I were going off of the diagram I listed above, then what do I buy to replace the piping going from the end of my H pipe to the beginning of the mufflers? Any help would be appreciated, none of my friends are into cars so you guys are all I got!