There are quite a few 'all season' tires still available, but if you want 'performance' or 'summer only' tires for 15" wheels, good luck. The difference may be hardly noticeable if you find tires with a soft rubber compound....UTQG of 400 is the best you can do on Tire Rack. (the BFG radial T/A is 400, a lower number is softer.)
edit: Years ago the tire of choice was Dunlop.....with a UTQG of 240!....sadly, no longer made for 15" wheels. Fieros love soft tires.
[This message has been edited by Gall757 (edited 12-30-2018).]
I recently went through this for my 88 GT. I did switch to 215 front and 225 rear some years ago. I decided to go with Kumhos and have been happy with the performance. I read in some posts that others had tried them and recommended them. Ordered them from tire rack and I see they are still available. I used to use Goodyear Eagle GTs on the car.