PTO cylinder burns hotter, recommended factory settings on highs should 1/2 on PTO and 0 on mag. On my 97' GTX I go 1 turn out on the lows and 3/4 for both PTO and MAG on the highs. I pick up about 100 RPM moving out more from the 1/2 setting.
I'd tune 1/8 at a time, I found that once I reached 3/4 or beyond it didn't gain anymore, so left it there. But I do run a 60:1 premix with the stock injection, so I may be diluting the mix at WOT, which explains why it runs a better top end turning out a little more on the highs.
If everything is stock including the airbox, you should use the settings as outlined in the manual.
High - 0 turns
Low - 1 turn plus or minus 1/4
Any richer and you will lose performance.