I have a 1998 F-150 with 4.6, manual tranny, with 4x4 shift on the floor. I am running 265/75/16 tires (factory was only 235's). Except for tires and a flowmaster 40 series muffler with short turndowns, everything on the truck is stock. I have the money to do one upgrade, any upgrade at all.....Any ideas what upgrade is the best for more power, better MPG......

 

Custom tune. $399 - $499 average, I love my PHP Gryphon.