AFAIK no, it wouldnt fit under my s4 as the back boxes are huge & the boot of rs4 is is different to cater for the exhaust, my mate did a 100% RS4 conversion to his B7 & when I say 100%, he changed everything except the V6 derv, they had to remove the whole boot shell to fit an RS4 version, to make the RS4 system fit 100%.