Just thought I'd lend my experience in case it could help someone else. Had intermittent very rough idle. Checked many things. Cleaned fuel injectors twice (once at dealer, once at independant shop). New plugs, checked cap/rotor and wires. Finally changed pre-cat O2 sensors and cleaned grounding point to frame. The grounding point to the frame is right under the condensation drain for the air conditioner on my truck. Don't know if it was the O2 sensors or the ground cleanup, but it runs much better now.