ok you need to learn alot about the engine how it works and so fourth, read this and try to understand as much as you can:
and the second page shows you a good way to find airleaks:
I hope this at least gives you a bit more of an insight into "how" your engine works, knowing this is the first step as you will know what *should* be happening when something is off, I have found that in most cases working out what is wrong is much much harder than actually fixing it.
as for take apart i just meant remove the engine from the chassis, you dont need to take the gears or anything else off the engine, and do the tests on the pages above to find leaks warning
if you take it off you will need to put it back correctly once fixed or you will damage the gears, I am guessing that your engine uses a gear not a belt to turn the rest of the drivetrain, and if so you will have to get the mesh between the gear on the engine and the other right or you will strip these gears in a very short time.
info on setting gear mesh :
this is quite brief, hopefully you will get the idea from this. if you wish to contunue using the car and having fun with it you will need to learn how to fix it, I admit just diving in and pulling it apart is a bad idea, and I think you need more help than what can be given on a forum, I can't really help you much more than this, if you use irc drop by #rc on efnet somebody will help you I guarantee it