also I believe, double check on this, the stock crank pulley is 2 pieces, with a shock absorbent rubber layer in the middle. This protects the belt and crankshaft from sudden jolts or something from either end, and underdrive ones dont, which isnt typically cool. And they do spin stuff slower. If you want more power and pull, lower your rotating weight. Lighter pistons, different compression ratio, lighter flywheel and or cam sprockets, pulleys, etc. Typically upgrading the plugs on a non-turbo with stock internals isnt going to do too much, but you may see some better results. There are mixed reviews on the platinum 4 prong plugs, for turbosI've heard many bad things, for NA's I've heard a 50/50. If you're gonna do anything, go with NGK plugs.
K&N, better intake "ram air" by sacrificing the resonator down there in the passenger fenderwall onfront of the tire and some home depot hose (cheap and it works) and ditch the silencer in the intake, check vfaq.com, that'll help a tiny bit.
Lighter wheels if you can, even if you're on steel ones, get cheap alloys. But less weight is good. Clean the throttle body, check the valve to make sure it opens 100%. That's on vfaq too.
Exhaust, but dont get anything ridiculous. You dont need much, a 2.5" mandrel bent willbe more then plenty. Any more dosent get you much for how much you'll pay for it.
Headers? Why not. Port the intake manifold whilst you're at it, and that throttle body elbow too. Round off the edges.
If you want, a small 50shot of nitrous can give you some oomph, butthat'll strain your motor, so you'll want to have it in good condition before you think about it.
That should be a nice hefty start. If you want, you can get an A/F gauge, EGT Gauge, and a S-AFC and try to tune/lean the mixture a little, but you wont see toooo much for how much you put into it.
You can always get a turbo