Ive a 2003 Defender 110 SW with 65,000 mile, Ive bypassed the mid box, back box and cat from the exhaust, making it a home-make straight thru system, Ive fitted a home-made egr by-pass, silicone hoses, and an itg air filter, and Im running 285/75 16 BFG muds and was getting about 27 mpg...