The tolerences on those little suckers are so minute, I have seen so many junked in the rc car department. Tuned pipe, change the compression by removing head shims or using thinner ones, more nitro. Knife edge the rod to cut through the fuel cleaner also helps.
If your going to break out the dremel I'll include a link, just try not to change the size of the ports, just make them cleaner, more angled on the out side. Good Luck.
I find the best way to port a 25 is by buying a 32 piston and sleeves cost almost as much as engines....figure that one out.

http://www.nascart.com/nitrom.htm