What mods/additions would you make?

[Pondrew]

No noticeable effect on anything other than a massive improvement in looks.

I heard you are still ugly, though! oke:

OP
Giving the brake calipers (and wheel hubs) a lick of hammerite does improve the looks of the car IMHO and it's really cheap if you DIY.
Also changing wheel bolts to either shiny silver or new black helps. BMW wheel bolts don't seem to stand up to our weather very well. Again cheap off the 'Bay

 

[Jasonn]

Ditch the run flats - put some decent rubber on instead - it's a much better car once you do that

 

[Busterboo]

Decent tyres and seat belt sleeves.

And add the Z4 off the boot to the bin.

 

[Mr Tidy]

If it is a manual get the Clutch Delay Valve removed!