A tip from my past experiences, tear the engine down, seal it up using gaskets and Permatex ultra copper spray gasket just to add insurance against air leaks. Port match your exhaust and the intake spacer as required , run VP 40:1 premix fuel, ensure you have the best tune, and that engine should rip nicely even with the stock exhaust and carb. There is NO magical bolt on mod that will yield big hp gains. While it's way cool to have tire shredding hp, you also need brakes to slow it back down, and the stock Rovan brakes and the steering are pretty pathetic out of the box. Took me some time , and got some suggestions here on the forum but I have my Terminator 5T dialed in nicely with a great all around compromise of great power and throttle response, and good braking and steering. Only engine mods I have are the DDM V2 silenced pipe (port matched) and a port matched DDM velocity stack, Screaming 13,500 rpm's straight into a tree or fence doesn't doo much good if you cant stop or turn...