This topic got brought up on another board. I did a little reading, and now I am even more confused....so I bring it here for the Rules Nerds!

The ITCS doesn't seem to mention anything at all about stuff like this. The only relevant stuff I can find is:

17.1.4.D.4
a "Any final drive ratio is permitted provided it fits the stock differential/transaxle housing without modification to the housing."
b "Any limited slip or locked differential is permitted."

c "No alteration to the stock transmission gear ratios for the make, model, type, and engine size of automobile is allowed."
I "think" this means one could do any of this to a final drive, as "Any final drive ratio is permitted". I don't think you could do this to the actual gears in the transmission, though. ????

Also of interest is the following:

17.1.4.D.1.q "The application and/or use of any painting, coating, plating, or impregnating substance (ie:anti-friction, thermal barrier, oil shedding coatings, chrome, anodizing, etc.) to any internal engine surface, including intake manifold internal surface, is prohibited."
While this doesn't specifically say you can't do stuff like cryo and shotpeening, I think it brings it into the "If it doesn't say you can, you can't" category, at least when you are dealing with engine internals.

"Rules Nerd" interpretations would be very welcome here.

Bowie
ITA Miata