lol, any catless exhaust with the tip too close to the bumper will leave your bumper covered in soot, actually. it doesn't matter what you're using to vent
if you use kartboy's longer hangers you don't have much to worry about. if you get the metal place that installs on the bumper above the exhaust tip, soot cleanup is quick and easy. the plate also protects your bumper from the occasional fireball (which EVERYONE running catless is prone to experience). tip placement is probably the one main factor in soot, as unabomber said. I don't have any trouble with soot, but i'm running a nur spec touring with the longer hangers.