Yes it Titanium exhaust is a thing. It's been a few years since I had to look into this but weight is lower than equivalent strength steel. Also heat transfer of Ti is lower than steel which should help keep more heat in the exhaust and therefore keep the velocity up for better flow/scavenging. Operating temperatures are slightly higher than stainless as well.

The real high end guys (F1 for example) were using high nickel alloys (such as the inconel referenced above). Or at least they were last decade when I talked to them, for all I know the new engine rules and turbos have forced a change to something even more exotic. My belief was the inconel was preferred over titanium due to durability issues but keep in mind those headers aren't much thicker than an index card.