There are also lots of "little things" beyond the commonly-listed changes that don't make it into the press releases.
Gen 1 NSX-R
- Many of the wire harnesses are different (i.e., lighter) because the car doesn't have power locks, audio, etc.
- Several of the harness plugs in the engine by are shielded against heat.
- The front brake dust shields are ventilated.
- The muffler is different (internally).
- The clutch pedal has a different geometry and engagement point.
- The left quarter panel is different (deletes the antenna hole).
- The rear spoiler is lighter due to thinner material and a different internal construction
- The engine is indeed balanced. First, piston/rod assemblies are weighed individually and matched to a very tight tolerance. Next, the entire rotating assembly (including clutch) is dynamically balanced. This results in a highly responsive engine.
- The ECU map is different. Timing is advanced in many spots (for use with JDM high-test gasoline).
- The tire compound is different for all available brands (Dunlop, Yokohama and Bridgestone).
- Alignment settings are different.
- Front and rear motor mounts use higher duometer rubber.
- Different left mounting bracket for the upper bulkhead trim (due to no TCS computer).
- Circuit-spec brake pads.
- A/C ducts have special shields.
- Rear chassis bar is thinner and lighter.
I'm probably missing a few things. Also, the heads were allegedly ported and polished by hand (along with the Integra Type-R's heads) in the engine assembly area at Tochigi. Another unconfirmed change is the throttle body does not have the TCS stepper motor.
You can do all of this to your US-spec NSX coupe, except for the wire harnesses. On my car, I went with CF side scoops and B-pillars to offset this weight difference.