I second that, I would bet money thats for a boost bottle. Boost bottles are fairly popular with 2-stroke motorcyle/atv engines, but have to be pretty carefully matched to the engine to work correctly. They are designed to prevent excessively uneven idle and low-throttle running as a result of a fuel/air "backwash" from the downward stroke of the piston. Basically, they store mixed fuel/air between the carb and the intake channel of the crankshaft and smooth out idle and low-mid throttle response. The idea is to get performance up before the engine comes "on the pipe" and the pipe starts to handle the fuel/air on the exhaust side. Like I said, it works well when set up right on bigger engines, but I doubt it will have much effect on an R/C motor.

As a disclaimer, I do not have an engine that uses a boost bottle, and nobody I race with uses one, so I can't say that i have any first-hand experience with them in an R/C application.

I too would save up the dough to buy the screamer engine and not waste cash on a cold-air intake that may or may not make much difference. Get a solid powerplant, get it tuned, and focus on driving skill, its free and it will make you a hell of a lot faster than a cold air intake will.