MobyRanger,
While it's not clear from your post what type of racing you're talking about, I'll venture forth assuming you mean street racing.
The one mod I've made to mine is the addition of a Halltech Tric. The unit gave me a measured SAE +10 rwhp and +15rwtq. I believe this unit produces more hp at speed, given the trap speed my car is making at the dragstrip.
The mod I'd like to do next is a set of long tube headers. This entails some trade-offs (noise, resonance, loss of the pre-cats) but should add an addtional +15 - 20 rwhp and rwtq.
These two mods ought not affect your warranty provided you have a good relationship with your servicing dealer. Ought not impact your car's reliability either. However, might wear out the rear tires faster, in which case your wife may say, "OK, MobyRanger, let's have the days."
Ranger