Just got hptuners this week for the GTO. Fixed some horrid fuel trim averages (+5 or so).
Got lazy and didn't feel like bothering with all the excel work.
http://www.tiggerfan.net/ltft.php
Just upload the csv file from hptuners and let it do the rest. Let me know if you'd like to see anything else there. Trying to build a reasonable collection of tools (Tracking KR etc) as I go on, but this one is just the first.
It may break from time to time as I'm tuning it as well. Price you pay for laziness