mx5cartalk.com

Remember an MX5 is a sports car, not a luxurious cruiser...

Yes, it's perfectly fine as far as I know. I got my 89' stock standard and straight away put Bilstein non adjustable shocks and kings springs lowered 1 and 1/4 inches. I wanted to lower mine 2 inches but my suspension guy told me not to as the shcoks would actually \"bottom out\" if I went any lower. A much much much firmer ride and I find myself constantly dodging any little hole in the ground otherwise there is an almighty THUMP and then rattling.
To me it sounds exactly like mine...It is by far the hardest and firmest ride I have ever felt and owned.
Hope this helps in some way.

I had the KYB non adjustable shocks on my car and found them way to soft. They had less control than the 80000km Mazda shocks I replaced. I doubt they would have any hope of controlling lower stiffer springs. I'm guessing you're probably riding on your bump stops. Strange as this may sound a stiffer shock may actually smooth out your ride by keeping the car off the bump stops. The KYB AGX adjustable shocks fixed the rough ride problems in my NA.

Also don't forget that unless you've added some, the 1990 cars have almost no bracing at all. My 1991 MX5 rattled a fair bit (on Konis and Kings) until I put the Mania chassis braces on - then it behaved a whole lot better. A cockpit brace of some sort (even a style bar) would probably help too.