True, but my car is sitting pretty low at the moment was also worried about clearance... Have been told that the 4 inch would flow a little better, however been making good power on my current 3.5 system so thought any increase in size will help free up things little.. My exhaust place was just concerned about clearance in fitting the twin 3 over the diff. Seen a few pics of the manta systems and it does look bloody close...