[genkichild]

I would do a full tune and see where you stand before starting anything at all. That said...
If your brakes shimmy, they are probably warped like my grandpa's records, get some new rotors and pads. AEM makes a big break kit that includes big rotors and caliper mounts, but uses your stock calipers. Better stopping power at about the price you would pay a dealer for small stock rotors.
autopower makes reasonably priced roll cages for teg's that meet SCCA approval, if you are going to the track.
Check the regulations of the division you will be racing in before you do anything, you may find something as simple as gutting the interrior and putting in seats will throw you into a modified category you aren't ready for.
Sucks you cant go above 4500rpm. Thats almost where it starts to get good. You aren't even hitting the vtec point.
You may want to see if the pained sound is coming from the exhaust manifold. They tend to rust and wear out around 100k and sound like a loud grating sound, like gravel on a vibrating tin sheet.
good luck