Found the GM 4-6-8 speed tranny book to be very helpful for a first time tuner although its a bit pricey @ $200...it does lack in depth details as some sections don't mention any explanation of what it does nor why it recommends certain values to be entered... only other criticism I have is the fact that it says to modify/disable TRQ reduction without any warnings while the HP software/guide clearly warns that it will break something/reduce tranny life.