I have a question about the 91 performance tune... I see everyone saying they use 93 octane with the tune. Is that a requirement for it? Problem is that 93 octane is not always available here. I've seen the pumps dry of 93 for two weeks, before. We only have two choices: 91 and 93. Often, the choice is made for us with availability.

 

91 is hard to find where I am located. Most places stock 87, 89, and 93. With the 91 performance tune you need to run at least 91. That's why I use 93.

 

I would run the 93 tune when the fuel is available, and run the 91 when it isn't. I re-tune my truck during fill up all the time. With a 25 gallon tank filled up from a 1/4 full, it barely takes longer to program than it does to fill the tank.