hi all. can anyone help. iv just bought my e36 bmw 328 which came with the original towbar i think.. in order for me to plug this in do i have to take the defuser off the back or can i cut it on the underside without it showing in order for me to use it. also the car idles perfectly but when i put my foot on the eccelorator just a fraction there is a slight judder although it is very slight and i am being a bit finnicky. just wondered what it could be. thanks all.