Well my next mod will be Ford Racing Headers. I was wondering if you guys had an dyno with headers installed before and after. my mods are in my signature. you guys feel any difference or have any tack slips?
All Mustangs come out of the factory with headers. Granted, they are pretty beat up for assembly purposes but they are still headers. You won't see any change in HP by swaping a shorty header for another shorty header...
The only way you would see a gain is if you had better flowing heads/intake that could take advantage of the slight increase in primary tube size.
Relate it to the install of your x-pipe or your cat-back. It will be alot less of an acceleration increase than you expect, but you'll get better gas mileage and it will sound louder/better. Just remember to get some good gaskets and tighten the flanges evenly. Otherwise you can just start calling yourself Captain Hook: the ticking drives you crazy.