Attached is a picture of the throttle shaft that I just removed from the 96 GSX.

On the spring side of the shaft is a black line of material and I can catch with my fingernail but cannot scrape off.

Question: Is this shaft supposed to be smooth from end to end ?

I know I am not to use any abrasive at all when cleaning this according to the posts and youtube video.

So I cleaned off the carbon on backside of shaft with my fingernail and can see
a clean line where the TPS side seal touched the shaft.

This black line looks like either a groove with an O ring that has gone hard or
a permanent ceramic ring molded in, or - left over from the original
seal on the spring side that might have stuck to the shaft.

Please tell me to clean this off or not, and if so, what to use if abrasive is not allowed. I considered a razor blade or x-acto knife .

Thought about PlastX or something like rubbing compound.

Bought new seals from MachV , was able to do the BISS o-ring from the box of spares from Harbor Freight.

So far so good. We are doing our first ever Boost Leak Test and just keep
working on each little thing.

You folks and this forum have been a HUGE help.