Sean,

What type of fuel are you using? Also, what is the oil content of that fuel? Those two things make a big contributing factor in your engine temps shooting up with just a small turn of the high end needle. Also, when you adjusted the high end needle setting, did you make a small adjustment on the low end needle setting? Some forget that when changing your high end setting you may have to tweak the low end just a little (low end is not set in stone). The same tweak may have to be done on the mid range needle as well (not set in stone either). Just curious to know what are the circumstances behind your radical temp swings.