I need some help, i just installed a magnaflow 2 1/2 inch cat-back system with 3 inch tips, before the install i would get about 300 miles out of a full tank of gas now im getting about 200 miles out of a full tank? my mods are upper/lower typhoon intake mac 1 5/8 equals 2 1/2 inch h-pipe, cold air intake. im running 93 octane gas. any help would be good.