98GTstang

i have 4.10s, x pipe, cat back exhaust, cold air intake, short shifter, king cobra clutch, found out that i dont have underdrive pulleys..lol just the stock ones..

Throttle Body/Plenum
Headers
Underdrive Pulleys

Which should i do next? or what should i do that i didnt list?

ROB 98GT

i was pretty happy with my march pullies, not bad of gain for the price. when the a\c is on or the heater is on when I stop it slows down a bit but i guess you have to lose something to gain power. if you get pullies make sure to get the NON-piggyback style. good luck.

GSXRIntensity

probably the pullies, &/or the t/b & plenum. Do the headers later unless you KNOW for sure you will be doing them anyway. I had a simple plan with my car....BUY EVERYTHING, but keep it N/A[]!!! It worked out.

ROB 98GT

also a handheld tuner is not a bad idea. i firmed up my shifting, bumped up the timing as far as it would let me + 94 octane and the car feels good. i felt more of a gain with the tuner against the pullies. diablosport predator works on 98's now and i'm pretty happy with it.

GSXRIntensity

I wouldn't recommend a tuner so soon, because there are lot of other things he could do first. They are definitely important mods, but tuners should be bought when needed. That's just my $.02 on it. I have an SCT flip-chip.

1BAD3V

If you can only choose a couple I would get the underdrive pullies and t/b & plenum combo. Wait on the longtubes' if you can, they give decent gains, but not for the money to buy and have installed. Do longtubes last or close to your last mod. And a Diablosport tuner will do wonders for you once you install the ud pullies and t/b & plenum.

nanaki

he might already have a tuner if he's running 4.10s. i'd get the tb/plenum and finish off your intake.