Finally the check engine light came on. Yay. Now I can get to diagnosin'!
Codes for random, and cylinder 1, 3, and 5 misfires. FUUUUUUCCCCCKKKKK
So to reiterate, last week I drove through a big puddle and it's been acting up ever since. It mostly runs and drives fine, but at times under a slight load (i.e. cruising) it will buck and lack power. Add more throttle, problem goes away.
So I checked the back three wires under the intake as best I could (YAY TRANSVERSE V6!), and found 1 and 5 not fully seated on the spark plug. Mmmkay. Can't reach 3. Pulled the wires back off 1 and 5, and #5 has some oil around the top of the wire boot. Not GREAT, but not BAD. The bottom of the boot was not wet, so the oil isn't LEAKING out, just seeping. I can deal with that. Cylinder 1 was dry as a bone. Got my long handled screw driver out to push down on #3, prying on the underside of the intake for leverage. It didn't move. BUT, out of the corner of my eye, something did. There's a nut on the side of the intake with a couple ground wires going to it. It was loose. Hmm. Tightened it up, but don't have time to go for a drive to see if its fixed. I also un-crossed the plug wires where they come off the front coils (front cylinders are coil-on-plug, with a lead going to the back bank), cleaning that mess up a bit.
Cleared the CEL with my phone (yay Torque app and $7 bluetooth OBDII adapter), and will test out my "repair" on the way to work tomorrow.