On engine teardown/ST build:

There definitely has not been a teardown in STR since it's inception, but there have teardowns in other ST classes. I have not heard of anyone doing a special "STR" s2000 engine build. Thankfully, the F20/F22 is already a work of art from the factory, so there is less to be gained by the type of stuff you mention compared to other engines. Additionally, and perhaps more importantly, the amount of power (250+) these engines produce in STR trim, coupled with relatively hefty 2600-2700 lb weight means that a 5hp gain means far less in ultimate lap time, compared to say a polar opposite 1800lb miata only making 125hp. And with straightline acceleration being a lower percentage of the lap than a road course, the impact per minute is less, comparitively speaking.

The "builder" classes where the car performance and setup (and therefore the importance of the speed of the car, less on the driver) is where you will see guys push the envelope with engine builds more. In those clases, especially street modified, it's pretty much a "run what you brung" doorslammer class, so nobody would ever care to check anyway.

Regarding coatings: the way the SCCA rulebook works, if it doesn't say that you CAN do it, then you can't do it.

 

Honda has done some of the low hanging fruit already, but they are limited by cost, durability, and warranty concerns. Most power generated is lost to friction; At S2000 engine speeds the return for many changes should be greater than normal.

But my point was your point..."with straightline acceleration being a lower percentage of the lap than a road course, the impact per minute is less, comparatively speaking.". HP is less important, especially in the small bits being talked about. The money would be better spent testing tires...which may involve a new question tomorrow