Thanks to everyone for the replies. The truck was running so poorly that I had to fly to Denver to help get him home. As it turns out, when the CEL came on, the truck would usually not exceed 55 MPH. Felt exactly like it was running in failsafe mode with the timing retarded. No power whatsoever and had to literally floor it to maintain any speed.

The ECU stored three codes:

14--Ignition circuit
41--Throttle position sensor
52--Knock sensor

We replaced the TPS and the coil, but truck still ran terribly. You mentioned that the knock sensor wire runs along the head, but where exactly is it? Left or right bank? Front or back? I'm going to try to look at this tonight. It's the only thing we didn't replace. Any idea of what one of these costs and is Toyota the only source for the part?

I made sure the mechanic used new headbolts, by the way. He already knew they were TTY in this application.