I have a 91 Mustang LX 2.3L and need some help with performance parts.?
Although I agree with quite a bit what cowboy has told you, there are many bolt ons that will help you out. If you enjoy the car, and are not looking to replace it, then by all means do what yor feel is right.
Exhaust will be you best start. There are so many different exhausts to choose from, and every person will give you what they think is the best. Try to jump on a couple of mustang forums, they often have sound clips with different exhaust set ups. Remember if you plan to remove your catalytic converter, you will have to either purchase mil-eliminators, or have your computer chip re-programmed.
K&N filter along with a cold air intake would be another great bolt on. Many cold air intakes will give you between 15-30 RWH. You can go further with this by purchasing a new throttle boby, intake plenum, and a new MAF (mass air flow censor/meter).
Rear end Gears: Although this will not add horsepower, it will get you from point a to point b alot faster. .373 gears are probably the most popular gear, and still works great on the street.
There are many other parts you can add. Look on some of the mustang forums to help you out.
Good luck, and keep that mustang alive.........