Still new to the forum myself and I may be wrong, but all you need to do is decide for yourself which tune you want or need based on the grade of fuel you run or want to run and what you use the truck for. My tunes were 87 performance and 87 tow leaving the 93 performance stock/canned tune as is for now. I believe the only thing that is recomended is if you want to order 2 performance tunes or 2 tow tunes that you space out the octane levels ie... 87 and 91 skipping 89 or 89 and 93 skipping 91. This depends on what grade of fuel is available to you. Also, almost forgot, when you order your tunes there is a form you fill out that lets you list all modifications to your truck and a box to list any that are not covered. It will ask for brand and model if you have it. It will also ask for your altitude which you can google ie... "What is the altitude of guatemala" and it should give you a range like 0 feet to 3000 feet. It depends on location and I'm pretty sure it really dosen't matter unless you are over 3000 feet which could make it run lean. Hope I have helped and not made things worse. Good luck with your purchase
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