I want to stay in H stock. From what I gather all I can really do is good tires, pull the air filter, and brake pads. Anything else anyone knows about that might help me?

 

You can put an high-flow air filter (don't think you can actually take it out compltely), a front sway bar (though I dont know if that will hurt the car more than help it), brake pads, a good set of adjustable shocks (i.e. konis), and a really good alignment to help the car rotate.

 

One of the most wonderful things about Stock is being able to run DOT-approved slicks.

Seriously, get some light wheels that are the same size as stock (13x5 on a DX? 14x5?) then throw some Kumho V710's on them and start reaping the benefits of grip.

And EK4 is right, you can't ditch the filter element, but you can run a high-flow element.

You can also upgrade your plug wires. Not sure if this will do a lot (I personally don't see a huge benefit unless your current wires are in need of repair anyway), but Grassroots Motorsports tested it and got a few extra horses out of a stock Neon. If that's worth it to you, then go for it.