I have a friend with a completely stock 99 gtp with a full stack on it. No kr at all with 5 added degrees of timing, stock was 10. Made a huge difference and is a whole new car. Nothing wrong with doing it. Headers should be thrown into the mix to notice even more gains with every added mod after that though. As to with a stock tune, my friends kr was completely gone and he noticed probably 15 whp tops. The tune was where the biggest difference of all was noticed. Tuning is everything. If you don't plan on modding anything further than that it would more or less just expensive.
