pressure wash. spray auto glym wheel cleaner on. work in with a soft brush. pressure wash. when the engine is still wet spray autoglym vynal and rubber all over......Looks amazing the next day. obviously cover any foam filter etc before u soak the engine bay
As been said already, I jetwash eng bay carefully after spraying Autoglym engine and machine cleaner on it, then spray AG vinyl and rubber care and just leave it to dry out with it running for a while.
I used swissvax motor shine on mine & it was one of the most impressive things I have used on a car.
The engine bay was clean & the car is quite new so it took little preparation & hopefully it will stop all the alloy parts going dry & "chalky"
It was a bit scary to use initially as it's like spraying a can of clear coat on your engine bay but it drys perfectly. The hoses & alloy still gleam like new.
I remember when I was looking for a GTR was that some engine bays looked a lot cleaner than others in the pictures & to be honest a "tarnished" engine bay put me off because I thought that someone who really really cared about the car wouldn't have let it get to that stage.