At the time I posted this article there were titanium heat exchangers for only a little more than 316 stainless. $170 vs $150. I know that titanium is now around $250, but I still might spend the extra for peace of mind. 316 stainless could be used, but I would want to make sure it is actually 316 and that it had been welded properly. Also 316 will eventually corrode, where titanium will last nearly forever. Basically titanium is overkill, which is what I wanted.316 SS is used in the hobby all the time. why does the heat exchanger need to be titanium? I only ask because 316 is much cheaper in price.