The best coil I have found is from the GP/Raider 760. It comes complete with wires & caps, & is a little pricy @ $200.
What makes it better is the wires. They are filliment core. They hold a better spark energy, with less resistance & don't break down over time, like copper core wires. If you ride salt water, this is definately the coil to run.
Std Yam & Kaw coils are the same, But if you look up the price of the kaw, it has a much better price point.
The MSD stock improved coil has a high failure rate. I have seen some that seem to last forever,while others are very short lived.
I have not seen a performance differance over stock with them.
ski ya, Paul