What idle-rpm and timing are you trying to run; it sounds like you have an engine torque issue, as in not enough of it.
The NSS is used for starting only, so it's wiring is not tied into the ignition circuit in any way.
As far as the ignition system is concerned,it doesn't care what gear the tranny is in.
I believe this is strictly a carb issue, with perhaps a bit of timing error thrown in, and possibly a too-tight TC.
Have you synced up the T-port yet, and if yes, what idle-timing did you get?
If it is more than 14*,then
Jack up the back with safety stands under the axle tubes, to get the rear tires off the ground.Then repeat the test. If it is fine now, then, there you have the proof that it's not wiring of any kind.
