i've used the stock plug and an OS 8 plug, both great. Absolutely no problem with either,so I would say from my experience OS 8 is a good bet (because you have low odds if your betting on getting the stock novarossi plug
). Mc 59's are very similar to OS 8's, but they are slightly more prone to deforming under heat and pressure so that the coil is a little bit more in the body of the plug then when it came from the factory. Even though, it is still a good plug, especially for the price.