+1. While the higher end SunTour derailleurs, such as a Cyclone or Superbe/Superbe Pro will be lighter, there will not be an appreciable difference in shifting performance. Additionally, the OP may also have to make a change to a closer ratio freewheel and shorten the chain, in order to accommodate the new derailleur. Personally, I'd stick with the current set-up until the OP has a few races under the belt and can decide whether it's something to pursue long term.

I've known several people who could churn all day long at 21mph but were lousy racers. They couldn't handle a bike, couldn't descend or climb, didn't have enough power to react to sprints or breaks, couldn't think under pressure situations, were nervous in large groups, etc. I'm not trying to discourage the OP. It's something he should definitely try, but it s not for everybody, for various reasons. I definitely wouldn't be upgrading, until I had a taste of what it's actually like. If, after a few races, I decided that I still wanted to pursue racing, I'd consider buying a more appropraite used bicycle, Financially, it makes more sense than constantly making minor upgrades to the current bicycle.