Cylon, First off the price seems too high for that coil in my opinion. in a few secs of searching, here is the same one for 23$ instead of 41 bucks, and it does not use a ugly pill bottle for the electro junction box.
But yes the stock CDi is probably the best and while some may disagree, most think stock is better suited for these small engines. That CDI is really just a pit bike coil I believe and the spark timing may be off for our engines. Certainly wont give 8-10 mph gains and may even run worse or the same. Anyone claiming a 10 mph without changing gearing is already suspect as throwing you total BS. Plus there are some inconsistencies from CDI to the same CDI, so its all a crap shoot on CDI performance anyhow. Too much controversy on CDIs and upgrades to them. Use the search engine to read reviews, tests, comparisons on CDIs. Some swear by the Lightning CDI?