not much for under 1k.
Gears are probably the best bang for your buck, around 250 for gears+master rebuild kit, and probably 350 for a install. with the other 300, you can find a used Xcal2 or Diablo handheld, you can install their tune, recalibrate the speedo to the new rear end, and play with their tune a bit if you know how to tune, and unlock a few more ponies.
1998 Eclipse GST Spyder - 14b turbo | 3" Catback | Evo8 BoV | 170fwhp if that
2003 Redfire Cobra - 448whp/435wtq - Sold