I had this same question when I placed my order i have the 4.6 with 3in leveling kit si/so borla exhaust and gotts mod intake...I asked Corey to ask the mad doc if the extra MPG or HP i would get between the custom 93 and custom 87 is worth the 30 cents more per gal of gas and she said he said NO
...I had already put on my order form i wanted a 93 custom tune and also a 87 custom tune. She could have just taken my money and been done with it but she let me know the 87 custom tune was great for MY MODS and i had no need for the 93 custom really(talk about customer service
). However like I said this was for MY application only and for what i use the truck for.