You clearly state the high idle did not begin until you adjusted the switch. You are breaking car fix rule #1, or 'look at the work'. Adjusting electronics often has another effect not planned on. Could be 2-3 things that happened there.
If you knew how many cars I have never seen before but fixed you would say nothing. I have never paid for a car repair in my entire life (40+ years worth) and a long stream of them and did not know a thing about any of those as well. They are cars, and that is good enough for me.
Up to 2000 hp. 200+ mph race cars and no formal training there as well. Self taught computer building, zero issues on a long stream of those too. Self taught ATX rebuilding, let me know when you catch up. Up to 10 types now I've never saw the insides of until I broke them apart, they all last at least 10 more years after it, I really can't say, one hasn't broken yet. I worked on two and spent up to $1 on each to get years more out of them as well, after I was told I needed a new transmission. Hilarious. CVT will be next and a leg up on them as I rebuilt that type drive 25 years ago all the time for industrial machines.
Ford changed TPS type on Focus cars to force owners to upgrade to a $300 new TB and different switch type, I created a mod that used a different TPS switch ($20) that modded easily in 5 minutes to the total cost of $2 more then worked perfectly to avoid that $300+ install thing Ford wanted. Ford TPS are not even settable, my modded one is. Other peoples' ideas had the same effect as yours, too high an idle and the ATX shifting totally screwed up. Mine works perfectly. Maybe I DO know a thing or 2 about TPS and effects? Nah, not me, I'm not smart enough.
There are so many non-OEM things and settings on my cars I cannot count, they run perfectly. Already working on relay changes in Nissan IPDM modules that 'cannot have the relays removed', same as the Ford CCRM and IRCM modules that cost $250 and I fixed for $5, it's funny. Ignition modules that change out for the normal guy for $600-$800, my fix cost 30 seconds electricity using a dremel and zero parts, the ignitions now have been working after they broke for years. I rebuild the $250 Ford PCM controlled alternators for as cheap as 30 cents for solder. Never more than $40-nobody showed me how to do that.
I'll leave you alone, you got enough issues as it is. I don't know spit about Nissans as well but I'm working on them and things go fine.
Luck............Skylines...........you act like they come from another universe...lol.