General rule for SHO's to undergo a tune up every 60 thousand miles. It includes new belts, filters, plugs, and shims to set the valve-lash back to factory specs. I'm not going to attempt it because I'm alot more familar w/ 5.0's rather than high output Yamaha engines.
To get a little better idea as to what all is involved with the 60,000 mile tuneup check out www.shotimes.com or cincy sho and even the sho shop, pretty much put a dot com behind the last two and that's their website. They are all very informative websites about the SHO's and all sell the 60K mile kit. Every time I see an SHO on the road I miss mine again, but this has also got me thinking again, is the same type of maintenance necessary on the 4.6 motors?