I have just bought a newer shape shogun after 7 old type 2001-2006 models,and have just fitted a unit, I did a before and after comparison, before the box was fitted it was showing 17 mpg towing a 750kg trailer,and about 15 mpg loaded with a car,with the pro-bitz box and with a 4 turn adjustment,it went to 26 mpg unloaded and 21 mpg loaded! the performance was instantly more responsive,even the engine note has changed,its really made a difference! i am so impressed i have just ordered a box for our bmw 530d estate 2004 model,as it is quite thirsty around town,and the box will pay for itself in 2 months! plus bags more performance!...its easy to fit and foolproof! and Im a car dealer! that says it all!