Mk3 and AR have a gear selector sensor which incorporates the neutral switch.

In the AR the ECU definitely changes its output dependent on the gear selected. It seems unlikely that this isn't also true for the Mk3.

There are three wires on a Mk3 sensor - green/black, green/yellow & green/red. From testing there doesn't seem to be any inter-relationship between the wires. There is infinite resistance between them and the engine casing (earth) except when in certain positions where there is no resistance. This happens once in 360 degrees for the green/black & green/red wires and twice for the green/yellow wire.

(Edit - After Looking at these results I think they maybe wrong in that it makes more sense if two wires have two points when the resistance is nothing. One of which works for both wires. Maybe I'll have another look sometime.)

Thats interesting what does the ecu change depending on what gear your in apart from ignition timing but thats more to do with rpm.

The AR monitors everything so you can see why that is needed.

All I can think is that the Mk3 monitors the gears to give a 'soft' hit of power in the lower gears so as not to break traction as easily . ECU changes ignition and PV opening maps as a result of gear selection . I've no evidence or articles to refer to .

Other thoughts .

I cant find the wires going to the gear selector on the mk3 wiring diagram. Am i lookin at the right one?

No they aren't there in any that I've seen. Maybe it was a feature destined for the Mk3 and they pulled it at the last minute . Or maybe the diagram is just wrong .

The AR gear sensor has 4 wires and is expalined on page 17-11 of the AR manual.

if anything like the NSR250's then if its CDI fed, there is a good chance you could wire splice to fool the CDI into thinking its still in second gear when actually in top to change the advance.

I've been reading that the ignition profile is changed according to each gear for acceleration/traction reasons but also engine/exhaust noise. Most power/torque seems to be created in 4th gear. So if you can fool the engine into thinking that every gear is 4th gear that should work fine BUT apparently the AR needs a special startup procedure ignition setting) in Neutral if my understanding is correct