Hot Rod Cams (with a good tune you could be looking at 30-40 HP) HR cams because you dont have to replace the retainers or springs or anything. Around 650-750 plus install
Longtubes.
Pypes is the best for the price on the S197 mustangs. My tuner said he gets more HP from those than almost all. DONT go with
BBK hes seen a loss in power. I personally like JBA but theyre about 750, where as the Pypes are like 500? Again around 20 plus horse
Shorty mid-pipe (will need with LT's) Pypes you can get the LT and X pipe for 600 new. Or I beleive just the O/r x is 240? online. JBA and
Magnaflow are a little bit more expensive.
Zex kit. As long as you dont run a huge shot it will be fine, also recommend the wid eopen throttle with it. 100 shot equals 100 instant horspower. about 6-00 for the kit plus install, and if you want the extras like the blow down valve which is a safety precaution and if you take it to the track they will make you have which is 100$, bottle heater which depending on where you love may be needed 300$, electric bottle opener which is just fun to have 300$, Purge kit, 150$, etc... All extras though
4.10 gears cheapest 150$ but install is about 300$ on top of that (Some like 3.73's but we havde 3.55's so its not that much of a difference, so if you dont want to go with something as steep as 4.10's Id suggest 1.93's but personally I think that 3.73's are too close to stock)
And then theres always the option of supercharfger which is always great but also the most expensive. lol
Dont do a throttle body, unless it is blown its a waste of 300 dollars. The tops youll gain is like 1 horsepower and I have seen people lose 5-10 (BBK) even with a tune
I have never had experience with this but its a cool option but not too cheap, charge motion delete plates.
And Ive heard both ways with underdrive pulleys. yes theyre only about200-250 and claim 15 hp. You wont get 15 horse out of it, or very unlikely and it isnt really good for you car though I know a lot of people that havent had a problem but also know a lot that have. Its underdriving your car which isnt good but yeah
And then a good radiator to make you run a bit cooler which is onlyu about 300 for a decent one