Hi,
I have used them, but not with the XT.
My gut feel is that they keep a consistant performance over a long time and really benefit a tuned bike (high compression pistons; high lift cams; etc...). Their cost makes them perhaps an expensive luxury and unneeded for the XTs level of tune - I'm sure somebody will have a different view though.
I think I will stay with the standard plugs.
Ciao,
Geoff
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