Blow-by?

[JimZ]

I've been reading up on blow-by in here, but I'm not sure if that's what I was seeing...
When I did a diesel purge this weekend, I noticed, sitting in the car with the hood up, that when I reved it pretty high I would start getting smoke coming from somewhere in the engine. It looked like it was somewhere around the air filter. Is this blow-by? Or if not, what is it and should I be concerned?

I'm realizing as I write this that I should have checked if that arm off the air filter is on there right.
Any thoughts?