My friend has a 91 truck 4WD 22 RE. It has a slight miss at idle, new Bosch oxygen sensor, valves adjusted, new plugs, wires and timed properly. Runs good except for that slight miss at idle, any ideas what it could be?

 

Two ideas, one is to check the TPS idle adjustments:
- http://www.4crawler.com/4x4/CheapTricks/TPS/index.shtml

And the second is the Bosch O2 sensor, they don't work well on Toyota engines, much better off with a Denso sensor:
- http://www.sparkplugs.com/