Yes the chamber serves to reflect the exhaust wave back into the engine at the rpm it is tuned at. A typical sled might work like this: clutch engages at 3800rpm. Pipe tuned for 4400 to 7000 peak HP. This way there is limited power at 3800 but enough to take off. Too much power and you just dig a hole and get stuck, or spin like crazy. Once you get going the clutch shifts up to 7K if WOT, and you have max power to however fast it goes. Now you put 300 picks in the track, then you up the clutch to 4500 engagement. Now it really takes off hard and pulls the front. Old HI-PO engines can be kind of all or nothing, but depends on how you do the clutch. I rode a friends 900 cat with 150 stock HP, a 7 year old could ride it all day if they didn't peg the gas. It was as docile as could be if you wanted, but did 0-60 in 3 seconds or so...it was hard to see. If you want the power you need the pipe. I would recommend you find a single pipe engine, and one from a trail sled not a race or high performance model....unless you want something special. Those 'normal' sleds will not have a peaky powerband, many twin pipe performance sleds do. Another issue is the pipe length is very important. You can turn the pipe, cut and weld it, but don't change the length in any section of it or it will change how it works. Most cut at an angle, then turn the pipe and weld back together, maybe multiple times but that way you can turn the pipe and keep it stock length and diameter. A pipe for low rpm will be longer, so if you shorten the pipe you tune it for higher rpm...it takes less time for the reflection to get back to engine, so it will work at higher rpm than before.