Starting from the top -

I know very little about cars. I just came into posession of a very well kept 1999 Chevy Prizm (Manual, 92k miles). For those who don't already know, it's very, very similar to a Toyota Corolla.

Now I want to start adding some aftermarket parts to it, but I don't know how the 2 cars are different.

I'm looking at Air Intakes, Exhausts, and windsheilds for the windows. I'm also looking for anything else you can recommend that may increase gas mileage or add to the longevity of the car. Please, I need your input. (I'm not interested in things that only add to HP unless it increases gas mileage as well or has some other benefit)

Are these all interchangeable between the Toyota Corolla and the Chevy Prizm? It's much easier to find parts for a Corolla than a Prizm and wikipedia stated that the 2 cars had the same engine.

Any advice would help. Thanks!

you have a much larger aftermarket with the corolla, get that unless you find a reason to do otherwise.

they're the same car

Ok, since it is essentially the same car, can someone please tell me what is DIFFERENT about the cars so I know what not to buy for a corolla?

Thanks for the help guys. You said little but I understand more now. :)

as far as i know the only differences are minor, badging and such. they're the same exact car, most everything should swap dirrectly.

http://www.cartalk.com/content/features/fueleconomy/

before 2003, same car. one says toyota, the other says chevy.

full synthetic oil. replace all fluids: power steering, brake, transaxle, coolant

K&N or similar drop-in air filter. new fuel filter. check battery, PCV valve, belts, hoses, bearings, struts, brakes, suspension.
an ignition "tune-up" would consist of plugs, wires, cap+rotor.

K&N or similar drop-in air filter

Ok I had one of my friends simply pop off the stock intake and slap on a K&N hi-flow air filter that would normally go on SRI or CAI. Instead he put it on the end of the tube that leads to the stock intake that's no longer there. Is this ok or should I go ahead an buy an SRI? (I can't find a cold air intake for a 99 corolla that's priced low enough to warrant the price)

EDIT: There was a piece of tubing that was filtered that was forced to be unfiltered due to there being no hole for it as there was originally.

I guess I'll go ahead and give this a bump.

as long as the air entering your engine is being filtered, there isn't an issue.