Not heard of problems with the series II OZ sport wheels but you never know. They are expensive - much more than the series I wheels.
Somebody in LOC had a series I with series II wheels. Never saw a picture - I think they have sold the car now.
I wouldn't. EGR can reduce engine power but Toyota program the ECU to compensate for it and by disabling it you may get too high engine temps. or get knocking which will be detected by the knock sensors and retard ignition timing (which will reduce power anyway).
This explains more:
http://www.autoshop101.com/forms/h61.pdf
Lexus haven't release fuel consumpsion figures. The 600 miles won't be on the combined fuel figure.
The engine runs all the time unless you come to a stop.
The 400h is not just about economy. It's also being sold as a higher performance RX.
Not really sure what you are asking. An engine swap? If so then you would need ECU, radiator, gearbox etc as well as the engine.
If you are thinking of selling you 300 and getting a 430 then I would say yes if you can afford it.
Not sure about the 1G-FE engine but nearly every other Toyota engine that uses a belt you just align the crank/camshafts put a new belt on and drive away - no engine damage.
The only one I can find is here:
http://www.parkingsensors.co.uk/taurus.htm
It hasa foil aerial - you really need one that will use the bumper bar. Rodders has one fitted to his GS.
They have some drawbacks - can be affected by rain and don't detect objects unless the vehicle is moving, but look much better than ultrasonic sensors.