Undoubtedly the condition of the electrical systems in each of our trucks is different, but in my truck the locks nearly shoot out of all 4 doors when locked/unlocked. I do not have the relay mod installed and the master switch is original and has not been cleaned. I do have Eric's headlight harness, but the rest of the electrical system is original. What made a huge difference for me is a combination of the following (1) new battery; (2) new Denso/OEM alternator; and (3) new battery cable set from "Fourrunner" here on Mud. In fact, I planned on doing the relay mod (even bought all the parts), but after installing the new battery and alternator, there was such a noticeable improvement in the operation of the locks that I abandoned the plan. Having said that, Fourrunner's battery cables are what really added the muscle not only to the locks, but the starter motor as well. The truck cranks with authority--big, big difference in starter performance!
I still have to take a day and do fourrunner's battery cable beefup. I've got a buttload of #1, #2 and #4 welding cable so I'll make my own, but this has been on the list for a while.