Uprated brakes, there are a few that fit from other cars but I can't remember which ones (sorry)
If you car has a distributor, they're worth picking up just as a replacement wear item
You might be able to make some money to buy mods by listing their parts on ebay since you have an easy time price checking, ECU's for these cars go for £40-50 (more for the pre-NATS) and scrapyards would probably sell them for £20-£30 since they're such a pain to sell (matching numbers)