ok so here it is i am thinking of some new up grades to my 02 2500hd chevy with the 8.1 and a six speed manual 4X4. i already did the tuner insall, i used a superchips tuner and tuned to 87 octane, obviously i tried the 91 octane tune, WOW that was fun. i installed a k&n drop in filter, stock replacement. i noticed some improvements, kinda hard right now since its been anywhere from ten to twenty below with out wind, and have to idle longer. any way i want to replace the drop in filter with the a cold air intake, keep the tune and replace the mass air flow sensor with a more flow one. i am really just wanting to see if anyone has done this or has any info. thank you. oh any good ideas on sythetic motor oil with this combo of uprgrades. thanks again