guess I will stick my .02 in .... OFF!!! my fastest times are with it off..... get all the weight off you can and work your suspension to get the launch right... as you can see there are a lot of opinions here. I say, watch your MPH to see what effects the tailgate ( up down or off ), mirrors, ( in or out, reduced or removed ), wipers and antenna, ( on or off ), better MPH indicates better areos.... I have found NO difference in 60's no matter what I did to the tailgate or spare. but that is my truck... check it on yours.... experiementation is the name of the game
TJ