I've used the fiberglass heat wraps with great success over the years. Mostly it was on headers. I never tried the titanium. On my TJ, I had a huge skid, It ran from just behind the oil pan to just past the transfercase. The cat was in there and the exhaust ran about two inch away from the trans/transfer. I wrapped the entire down pipe all the way to the muffler including the cat. I ran that for seven or eight years will no ill effect. I did peel it off once in a while to see if the exhaust pipe corroded which it didn't. I also saw no difference from my cat output on the smog machine. I was afraid it would run hotter and possibly even clean up my emissions some but no.
On my old tow rig, the headers would glow bright red. Those I had wrapped for easy ten years with no effect on the headers.
I see people talk about their exhaust corroding from the wrap. I cant say either way because I live in a dry climate. On my TJ I was paranoid which is why I peeled it off a couple of times. I do have friends with race vehicles and a couple of motor cycles who run the titanium with no ill effects that they mentioned. On both my tow rig and TJ the wrap was stained from mud, especially the TJ.
If you read what the wrap manufactures say, they talk about increased exhaust flow do to keeping the heat/pressure contained. One of my buddies runs a pit crew on a few track teams. We talked about heat wrap to great length. His comment was, most of the cars they run have it and if it makes a difference in performance, its slight and the drivers haven't seem to notice. It does help when working around hot exhaust and keeping the heat away from the cab.
All in all, none of the people I have encountered noticed any degrading of the metal from moisture but again, this is in a moderately dry climate. I personally wouldn't hesitate to put it on anything.
