I currently have the 87 tune installed. Do I have to reload the stock tune and then do the 91 or can I just load the 91.

 

you can just load the 91 but be sure you have 91 or better octane gas in the tank before you do.

 

yup what my brother said ^^^^

 

Just load it, no need to return to stock.

 

^^^^^echo^^^^^^

 

I was too lazy to read the other responses before I responded

 

haa haaa lazy *** teach lol

 

Thanks. I will be loading up with the 91 on Friday

 

Good words. Up here in northern Utah, we are over 4700 feet in elevation, and the min grade is 85 octane. (Engine octane requirements decrease with altitude, I'm told) However, when I loaded the 87 tune, I could hear the engine knocking when going uphill. Had to fill up with 88 (mid grade here). So, make sure the grade matches your tune....