Sorry for your troubles; I can empathize with your pain. I cannot recommend enough Vredstein Ultrac Sessentra tires in OEM sizes for your Z. Have had them for two years and have won several autocrosses against Vettes running tires costing 3 times as much! They are ultra quiet, smooth riding like on air, and show no wear with a 300 tread wear rating. They have a cool rain dispersing tread that plowed thru 2" of standing water and wet grip that is confidence inspiring. Can't say enough good things regardless of price - about $800 shipped for 4! Available here and 4.8/5 ratings from users:
http://www.performanceplustire.com/p...ck-to-top-link