Yea guys i tune my truck back to stock to tune it with 89 tune but my cortex superchips doesn't have it. It only has 87,91,and 93 tune. But i had put 89 octane gas on my truck to tune it with the 89 tune, but i didn't have a option so tune it back to 87 tune, will i come across problems if i keep putting 89 octane on the 87 tune? or should i waste the 89 gas and stick with 87 octane gas? thanks everybody, for the help.