Ive used Toyo's on my MX5.......probably the most recommended make on the forums for those...and been very pleased with them.
I questioned the choice of tyres at the factory once and was told that Conti made them for the factory...certainly I've never seen them for sale anywhere.
Have them fitted to my MX5 as well, and I am really impressed with the roadholding and the wear rate seems more than reasonable.