I've been doing some research on my WR450 "stutter" issue. So far, I've found lots of statements that the grey wire is a CDI map-limiter to "de-tune" the WR for several reasons: trail-power, emissions, and lower rev's for dB's. Reasons vary some, but the common response seems to be that when you cut the grey wire, you access the YZ timing map in the CDI. OK, fine......... IF this is the case, what's the mechanical difference between the YZ's and WR's that would make them run different (other than the needle)?