i have the MAGNAFLOW exhaust on my truck i took both of the resinators off.IT alsohas aCAI on to but i notice that whenever i put the exhaust on i lost some back pressure and notice lost on MPG and all of my drivin is still the same as it was before i put the exhaust on. Wenever i just had the CAI and stock exhaust i was gettin better MPG. Is that how it is suppose to be

 

u have a Magnaflow cat-back exhaust? or just universal magnaflow mufflers?