My IS is normally 2 to 3 mpg over, similar to any Toyota/Lexus i've had in the past. If you click on my Fuelly link, the notes against each fill-up have the readings from the fuel computer and fuelly has the real readings.
Mine has been doing this for a while now, although seems to be getting worse just as my car has gone out of warranty :(
Doesn't do it enough yet to be able to locate the noise, I suspect it is one of the air diversion flaps.
Welcome Kevin. With only around 600 GSs sold each year in the UK you have some exclusivity but with that comes a lack of information about them. Look at US forums as the GS is sold in much greater numbers there.
here is the wiring diagram from a 2001 model - sounds like the circuit is the same.
Does the heater relay look original? Sounds to me as if it isn't the correct one and is working in reverse - i.e. normally closed is connecting to the heater fuse rather than ground.
It has a different headlight design though. Obviously a vehicle can have full LED lights, Lexus and Toyota have vehicles that do, but maybe not with IS design.
Depends on your dealer. I've never had a CT from Lexus Guildford, either IS, NX or RX - they seem to provide a like for like so I mainly get an IS these days. They probably do have CT loan vehicles but I guess they are given to CT owners.
There isn't the market for these parts currently in the UK - the Gen 3 IS is mainly purchased by leasing companies/company vehicles or people that aren't that interested on modifying their vehicles. Typically things change as the vehicles get older.
At the moment you will probably have to import yourself.
Toyota charge £100 for their map updates - which is exactly the same thing. I guess they feel Lexus owners can afford a 50% premium.
Toyota also provide 3 years of free maps on their top grade vehicles. You just download and apply via USB memory stick.
The old loan system was on the old CD based Nav systems which couldn't hold all of Europe. As the DVD systems come with multiple countries this isn't needed anymore. It was never a way to obtain new maps updates.
Grip should be ok, if not better, but you will wear the tyres and potentially stress the sidewalls. Another issue with running low pressures is you are likely to damage your rims if you hit a pothole.
Even worse is the fact that the seats probably don't contain the positioning sensors on them, so you would need new seats, wiring looms, seat/door ECUs, switch gear and trim panel.
You can play music via USB from an iPhone because it will be detected as an iPod. For an Android phone it would need to present the filesystem as a USB mass storage device for the car to detect it properly. If your phone cannot do this natively there are some apps the allow this but they seem to be model specific and have other restrictions.
It should be at operating temperature and the level checked with the engine running, having first shifted through all the gears to make sure the fluid has filled the valve body of the transmission.