The IDM is actually meant to get wet, water can
get in there (mostly through the "breather) but, here's where I would start.
The "Insane" idle is probably what it sounds like running on 4clys.
You're right, the AZ scanner is useless - return it (but, so are most others gonna be too - you need a professional scanner or an AutoEnginuity) You do
have codes (probably P1316) and a Buzz Test, performed by a good scanner, would help you out.
So, when it's Cold, start it up, run over to the top of each tire and put your hand on the Exhaust Manifolds (cold engine - right?). I think you'll find one side warming up and the other Not. THAT would be the Dead side...
You could look into the IDM plug maybe, see that it looks dry at least, but other than that, there's not much you can do at this point (you could try opening it, Very Carefully if you expect to use it as a core, but not much chance you're gonna be able to fix it yourself)
Next pull the ValveCover on the dead side and get a close look at the UVCH connectors In & Out. See if there are any burnt pins or evidence it's unplugging. IF NOT, I'd be thinking IDM
Here's a good vid -> http://www.youtube.com/v/GHwjEfJtM_g&hl