Ok, so I'm rolling along in my baby Duramax Colorado doing between 35-45 in fairly heavy traffic and I smell this horrible smell like I'm following a poorly running public bus or quad axle dump truck. Then, as I travel along basking in the essence of that foul smell from the nether regions of perdition, I realize some 10-15 minutes later that this may be the regen I hear spoken of. Oddly enough, it was running fine and had good power. By the time I was on the home stretch just a few minutes hence, the smell was gone. Weird.