It is definitely titanium, that isn't at issue.
It definitely isn't a Litespeed, but it could have been made by them.
The canti bridge looks like a Litespeed canti bridge, but other builders may have copied Litespeed bridges (or possibly bought bridges from Litespeed)
The cable stops don't particularly look like Litespeed ones. The formation may point to a particular brand that commissioned the frame, but I don't know which.
The chunky brake post mounts look a bit like Litespeed ones, but I'm not sure if they ever had flat sides like that.
The CNC dropouts are a sophisticated touch. Litespeed didn't use them before 1994, and then only on the higher models. Merlin used them earlier though, so they don't necessarily date the frame.
Merlin did make frames for other brands, but not to anything like the same extent as Litespeed, and I don't think Merlin made your frame.
Nobody used canti bridges like that after 96.
The top tube routing for the front mech but no pulley at the bottom of the seat tube must date the frame to 93 or later. Top-pull mechs only came out in 92 and weren't that widely available, so early top tube routed frames had a pulley so that you could still use a down-pull mech.
I don't know about Mongoose, but it isn't an Orange.
Orange Vit Ts were made by A-Pro, which I think was the only Taiwanese builder making titanium frames at this time, and I believe that all A-Pro frames have an A serial number.
The exact weight combined with the dimensions (c-t seat tube, c-c top tube, head tube) could help indicate what kind of frame it is.