Finally got my Tau Codex. As is my wont, immediately found a bug :/
The rules for the Disruption Pod (CTE p.72) say it gives +1 to cover saves. Nice and simple.
Unfortunately, in the summary pull-out at the back, it says they confer Stealth.
The problem here is that, as I read it, Stealth can't stack with itself, so if you have Night Fighting up and are at Stealth range, one version gives you an additional +1 to your Cover Save, and the other doesn't.
Of course, this is less of a problem if I've misread Stealth itself (BRB p.42). It says that bonuses from Stealth and Shrouded are cumulative, but I'm not sure if that's meant to mean Stealth is cumulative with another Steath from a different source.
Gah, I've gone cross-eyed.