http://www.pro-touring.com/showthrea...(-back-purging)
heres a great thread regarding stainless exhaust. I run a separate tank and regulator to purge it. Temps are 29-38 on my Miller 180 SD tig.
Its all in the prep. Get your joints nice and tight. I get lazy sometimes on fitment but I can get by. For me its easier to TIG weld exhaust thank MIG. Slower but easier.
Practice-Practice-Practice