This thread describes exactly what my truck has been doing: http://wew.ttora.com/forum/showthread.php?t=13283
I have found no evidence of a vacuum leak, but I have not had the time to troubleshoot the rest thoroughly. I'd be fine with the TPS going bad, but I haven't gotten a CEL, which normally accompanies it. I'm really hoping it isn't the APPS, since the part, unlike the TPS, is only available as part of the complete TB (~$800).
No deep water, but I still need to pull the wires and plugs to inspect. Plugs are only a few thousand miles old, but wires are original.