1. 20" FE alloys - generally regarded as improving the looks significantly, but pricey (probably £700+ for the alloys, plus more expensive tyres). A number of us run 20s as summer wheels, with (original?) 18" as winters.
2 - Solar sunroof (if you don't already have one..). Great for keeping the cabin cool in the summer (i.e. now!
.). Can be had for c.£200, though fitting it is a bit tricky - there's a thread on "how to" on here
3 - Audio upgrade: to RNS-D/Bose (if you don't already have that), or to RNS-E if you do. Both make a significant difference if you listen to music much.
4 - Exhaust upgrade to a Miltek (or similar). Costs about a grand new and fitted, I think, and this is the one upgrade I'm still waiting to do. These are harder to get hold of these days for S8's, but can still be done (hopefully!)
5. Engine chip/upgrade - there's a number of these around, but they generally on the D2 tend to make the engine more tractable/smoother, rather than upping the power, but others may advise otherwise.
There are loads of other mods you can do, and this forum is full of them - as stated in the previous post, as well as getting general advice, you may want to decide what area you want to upgrade, and then look at the threads in that area. Whatever you choose to do, it's all part of the fun of 8 ownership, and somebody here will be able to help
