Hello everyone my name is Bryan and I am new to mustangs and would like to know what is the best mods to do to a 1998 gt it has the 4.6 five speed already done to the car is cold air intake diablo chip and three inch exhaust any help to this will be highly appreciated thanks in advance Bryan

Welcome to the site!! I moved your thread for a better response.

Really depends what you want out of the car and of course budget.

Rearend gears and suspension mods like lower control arms are always a good start and bang for your buck. If you want any real power out of it then PI swap, which is the heads and intake from a 1999+ Mustang. Beyond that, once you get into the bolt ons many of them aren't as effective as their advertising suggests - some are still good but at least a few are completely useless. Kind of a broad subject for me to attempt covering in a single post, but if you do a little looking around on here (search button) most of this stuff has been covered ad nauseum. Whatever you can't find, feel free to ask.