Having recently got a TM pistol I'm doing a bit of an experiment, so have a few different gasses ordered.
When my FNX arrived I loaded a mag and chrono'd it on the gas that was in it on arrival. First shot was 293fps / 0.80j then a steady 270 / 0.7 (ish) until it ran out after 12 shots. So then I lobbed some Abbey 144a in and it averaged around 240fps / 0.53j, which made me think that TM aren't using a particularly low powered gas when they are making the mags ... so does that mean the pistol's built for stronger gas or do TM just use whatever gas they have at the factory to test fill their mags on manufacture?
Then there's comments much like those on here where people have been happily using green gas for years with no ill-effects on the pistol.
Long story short, I've got small cans of Abbey Ultra, Nuprol 1.0 and Nuprol 2.0 on the way and I'm planning on seeing what kind of power difference I get between them. Will see where we end up in terms of the gas I use long term after that.