97 SL2 performance question

Hello all. I got my 97 saturn sl2 about this time last year, and have
been wanting to milk some more power out of it. My problem is, I'm a
poor college student, so it has to be on a budget. So my question is
this: What is the best way to get the best performance boost for my
buck?

Here's what I've done so far:

Custom intake system: clamped a cone filter directly onto the throttle
body

Custom exhaust: This is a do it yourself at AutoZone hack job. I cut
the pipe after the cat and fitted the pipe diameter to
2.25'', threw on a glass pack, and side-piped it (sorry no pic with
me).

Better Tires: Yokohama 205x60xR15

The other thing I've heard about doing is placing a resistor between
the two contacts of the IAT sensor, but have always considered it chump
change. Am I wrong?