butt welding exhaust system

I'm not the welding expert, but I like a tight joint. No penetration issues with the TIG and not as much filler needed if any. I'll say though, I don't think an exhaust will be taking enough abuse to kill any half way correct weld from any welder. Some guys just like to criticize everybody about everything, gives them a purpose in life or something.

I've never heard of back purging with mild steel, but again, not the expert. I can't justify an extra tank so I use Solar Flux when welding stainless tubing, works like a charm.