Titanium exhaust?

People don't want to spend $$ on light weight wheel which would have at least 5x the effect of a titanium exhaust because the weight saved is rotational and unsprung.

A lithium battery saves more weight for less cash (in a better location).

Thin wall stainless is already pretty light.

Titanium exhaust should not be high on your list if you are concerned with performance but aren't made of money.

If you look at bicycle frames, Titanium can't realize the weight savings that its density suggests even if they use $$$ double butted tubes.

In an exhaust system, the difficulty of welding thin tubes might negate the weight savings compared to thin wall stainless if you use thicker wall titanium tubes.

A bigger issue is the muffler, there are just more options in stainless, including very light weight designs.

I think 321 stainless may have superior fatigue strength which is important in a system that has thin walls and gets heat cycled.

Finally, the welding process for stainless is not nearly as complicated as Titanium, you just need TIG and a back purge, something I can do. Titanium needs a helium purged glove box I think.