This maybe common knowledge to most but thought I would share. Over the last year or so my 1kz-te engine had been reving occasionaly, at idle, between 400 and 800rpm. After going through the fuel system the problem still persisted. Finaly 1 month plus ago the fuse on the battery terminal blew creating puff of smoke from the engine bay. The problem was finaly tracked down to a dodgy Fuel Spill Control valve on the electronic fuel pump. The fuel spill control valve is located on the rear on the pump and has a 2 wire connector, (can't post the pdf I have as network does not allow access to photobucket). A faulty Spill Control Valve can be identified by using an ohm meter. The open circuit, without the wires connected, ohm reading should be between 1 - 2 ohms, ideally 1.4ohm. The dodgy one on my pump was reading 24ohm. The whole pump was exchanged at the the time and the engine is now running very well. Exchanged at the time as was quite some distance from decent workshop facilities. Now for the interesting part: The 1kz-te fuel pump spill control valve is also the same as can be found on the 2lt-te fuel pump. So for those who suspect problems with fuel pumps, check the Spill Control valve. Signs for bad Spill Control valve: 1. Difficult to start. 2. Horrid smog emitted from exhaust on start up. 3. Erratic idling. 4. Blown fuse on battery side. 5. Not too sure on this one, still to be confirmed. Battery drainage. Above 5 points were are as I had. Hope the above will be useful.