The best jetting I have found at our altitude at 85 degrees with the airbox lid off is:

170 Main Jet, 50 Pilot Jet, NDSR needle at #4 down, with 2 turns out on the idle mixture, and #50 leak jet.

Warning: 

On all 2006 YFZ450 engines that I have checked - There are 2 bolts loose in the engine. They are located in the left case cover behind the starter idler gear. Below is a photo of 2 bolts just like I found them - to fix this you need to remove the 2 bolts holding the starter idler cover on, remove the cover and idler gear. You then need to torque those bolts to 85 inch lbs. Thanks to a good customer - Peter Bassage from the UK -  for bringing this to my attention. Please pass this information on to as many people as possible the have a 2006 YFZ450.

Patent Pending

Rear XC Linkage - This Linkage is newly designed for the 2006 YFZ450 to work with the stock shock - $225.00

Rear MX Linkage - This Linkage is newly designed for the 2006 YFZ450 to work with the stock shock - $225.00

Clutch Fibers - These fibers are more consistent as they heat up and also give better clutch release for less stalling - $11.95 Each

Rear suspension package - Includes revalving your rear shock, a new link , and a new rear spring - $395.00