UPDATE
E53 4.8is
This went into Owen Garages to have new rear arms, lower rear ball-joints and front steering arms and track-rods. It then got an alignment. After picking it up it drives much better. So I wasted no time fitting the spacers I'd bought. I went with H&R as I've used them before and the quality is very good. They're TUV approved which means they've had some level of quality assurance which seemed important to me for something that'll be holding the wheels on a 2-tonne truck.
I put 25mms on the front and 30s on the rear, so widening the track 50mm front and 60mm rear. I think it looks much better with the wheels pushed out filling the arches.
Pleasingly it seems to drive better too. The spring rate from the air-springs seemed a bit high running the ride-height lower than standard. The spacers will be reducing the effective spring rate slightly.
I then de-badged the rear and gave it a thorough clean. I focused on getting the plastics back to a deep black too.
At this time of the year it obviously got fairly filthy again almost instantly. I think it's really looking a lot better than when I bought it though.
I wanted to add some of the functionality that my E70 had. Some simple things like triple-flash indicators you miss when you no longer have them. So I fitted an Intravee unit which connects into the car's loom and intercepts various signals and can modify them. I added the triple-flash indicators, but also fold /unfolding mirrors and follow-me home lights on lock / unlock. Auto-lock on drive off, SMS handling to the phone interface, PDC distance display, voice control and a few other things I can't remember. I connected the Intravee to an Alpine iPod interface too that does full control incuding track and artist display on the dash and full control from the head unit or steering-wheel controls.
It interfaces to the car through the CD player plug, so the CD changer is lost which is no issue at all for me. I wanted the components to neatly mount into the rack in the boot where the CD changer had been and for the wiring to all be completely hidden.
The hardest part of which has been getting the cables behind trim as it's all so ridiculously over-engineered and every part has a mass of fasteners and other parts that have to be removed first. Even this bit of trim in the boot took almost an hour to remove and get the cable behind.
It all fits very neatly though. I'm going to fit an inverter and UK 3 pin socket to the right of where the Apline plug is currently entering.
So far the cable exits under the rear seat so the next job is to get it under the carpet, through the centre console and up to where I decide to fit my iPhone mount.