What difference is there in the porting between the MC18 and MC21/28, and what differences does it make to the power delivery?
I have just gotten an MC21, but I used to race an MC18, and I would like to know what differences there are.

Also, are the MC21 chambers restricted compared to the MC18's?
I know that the MC18 chambers are pretty good, just the stingers need replacing with blow throughs. What are the stock MC21 units like?

If you know any dynosheets, point me at them
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The Chopster