Sorry to hear you have been having troubles with your Iolite, I have one and it is my main smoking device.

Sounds like you have tried it extensively, but just a few thoughts from my experience with the piece.

The majority of the time I do not get visible vapor after taking hits but still get the full effects.

As others have said the higher quality butane does seem to make a fairly large difference but even if it is cheaper butane it should still work in my experience.

Generally when going to a vape session with the Iolite I'll load it up and let it heat up for a cycle and then start hitting it, I usually hit it for 10-20 minutes.

Good luck trying to get it to work it definitely has a bit of a learning curve to it.