Alldalights my thoughts also.
Definitely interested in a stainless sports exhaust mainly for the weight saving (original is a huge weight compared to the thinner stainless steel).
Saw a company on eBay which looked good quality and price
https://www.ebay.co.uk/itm/BMW-Z3-Custom-Build-Stainless-Steel-Exhaust-Cat-Back-BZ301/162638054054?fits=Car+Make%3ABMW|Model%3AZ3&hash=item25ddfbc2a6:g:gXYAAOSwgyxWXc9n
You can even choose the design and sound of the system as they build it for you there and then for £280 for a Cat back system.
Will probably go there once lockdown is all over next year and at least that will be a good start.
After that, was thinking a few bushes but too many as can stiffen up the suspension a little too hard for everyday road use.