snub disphenoid

I'm pretty positive this is just excess gas being burned off inside the exhaust system, but I thought I'd double check with anyone on here.

When being pushed hard or revved, my car pops when I shift or let off the throttle. I've seen several other cars do this on a dyno (a lot more than mine), and I also saw a flame-shooting VW Corrado do this as well (before it ripped off a salvo of pops and flames - naturally, without a kit). This isn't necessarily a bad thing, is it? The engine was completely warm and all. I guess I'm just running the car a bit rich, but since I still have (one) cat in place I don't think it's shooting flames or anything. I dunno, anything particularly harmful that could come from this?

http://www.imagestation.com/album/?id=4287377813 (third video, labeled RB->Miller->HKS)