the total length of the exhaust does affect the timing of the return pressure waves that stop fresh fuel charge from going straight out the exhaust ports.

I remember reading that Tyga pipes have a tuned length that specifically suits the 250cc motor - therefore they are not the ideal length/size for use with the 300cc kit. Though i have no idea just how much of a difference an increase in stinger length would cause to your r5k's power output. My 300 certainly pulls hard enough - even if the pipes aren't specifcally tuned to the motor's capacity.
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