Well since we're talking MX-5s
Mine's buried in this thread already somewhere but I've just put a twin exhaust on it so it sounds like it should have done in the first place. I love it - tunnels are glorious
I've also replaced my tired old suspension with adjustable shocks and stiffer springs. The ride is massively improved and there's more grip but it's lost some of its responsiveness so I'm still getting used to it. But that's the beauty of adjustable shocks, I can change it in five minutes!
I haven't been on track with the new setup yet but I accidentally entered the supermarket car park in a neat four wheel drift last week. I got caught in a torrential downpour with the roof down, so was trying to keep the speed up to keep dry. That first exploration of the new limits was most entertaining