There isn't a whole lot you can do to make the OS Surpass more potent than it already is. But there are things that can be done. The easiest modification is to lower the compression and raise the nitro content of your fuel. This will get you another 300 to 700 RPM on 30% nitro. This works well.
Ceramic bearings with get you another 100 to 500 RPM but more important, they won't corrode. Ceramics are Lighter, Smoother, and Faster than stock bearings. This will be an expensive up-grade though.
Gas Porting is a good modification that prevents loosing horsepower. It uses compression to force the piston ring to seal against the cylinder. You perform this mod to the OEM piston.
Notching the upper ring groove in 3 places will get the job done, as depicted in the photo. The Oil Slot doesn't add any horsepower. But it does allow for better lubrication especially at higher RPM's. There's a small bypass hole located at the top of the slot. The down-stroke of the piston forces the oil vapor into the slot thereby lubricating the skirt.
Running a straight pipe in place of the muffler will yield another 200 RPM depending on the fuel used. This is a cheap source of horsepower. Surpass engines aren't loud overly loud so running a straight pipe usually isn't a problem. You can tap the pipe for your pressure fitting if you like, but four strokes run well without it.
The most potent modification you can do to the Surpass is put a big two stroke carb on it. Not only will you get more power, the throttle accelleration is mind boggling.
This is a difficult modification, but worth the effort! A pressure tap to the muffler is required in order to get the fuel to the carb, only when the engine is up-right. This mod really cranks out the horsepower.