Playing with the TSP sensor and using your seat of the pants feel to meter it just doesnt sit well with me. Hooking up a throttle meter, 02 bung, and timing gun to make your adjustments sure does though.
Firstly mcg : Glad you got to the bottom of your issues
Im in the UK, and our bikes don't have all the smog stuff you do, so i didn't have that to contend with.
My bike also came to me with an FMF, but i didn't care for it and went back to stock. I've also never suffered any low-down issues you describe and mine has always pulled strongly and cleanly from low down. My only issue was the flame-outs, so perhaps your symptoms and problems were slightly worse, or at least slightly different to mine ?
All i can tell you is (And although im a mechanical Engineer, im certainly not a Automotive or Electronic engineer) i imagine the slot is put in the TPS; exactly for the reason of fine adjustment. And i can only imagine KTM wouldn't put enough adjustment in there so that a lamen (Or infact anyone) could do irretrievable damage.
I see it as akin to turning the distributor cap on a old car to finely adjust the timing. And having to listen for a happy engine is hardly 'seat of the pants'.
How do you think mechanics have been tuning combustion engines for the centuries and decades before O2 meters and electronic timing guns etc ?
All i can tell you is; for this bike, in this climate and during the last 100 miles covered yesterday afternoon and this morning: Its now running like a dream and to date i havn't had a single flame-out or hiccup from cold or otherwise.
I've also since lowered the tickover back-down, to a really solid, thumping idle as it appears to be fueling very well and doesnt need the additional 'back-up' of a slightly higher tickover. To be fair this was only ever MY 'insurance'.
Until something changes im one very happy camper right now, as at first the issue with the continual flame-outs was quite concerning, and the difference to now substantial..........