I quote
" Putting your GTP into "Performance Shift" mode raises the RPM level at which the transmission shifts into the next highest gear, and may allow your RPMs to go a bit higher than in normal mode. Use it for getting up to speed more quickly, passing (except when in 4th gear; it won't help here), racing, etc. According to those more sensitive to the shift characteristics, "Performance Shift" mode feels quite a bit more firm and quick during shifts than normal mode."