Purchased my '98 1.9 in March and the first week driver's side rear tire had a slow leak and bad valve stem (Michelin Pilots). Today about 10 minutes after I parked the car air started streaming out of the passenger front stem. I am ultra careful with the tires/rims--no scratches. Anyone else have this problem?...should I expect more of the same with the other two? Suggestions? Enjoy MB--1st time post. Thanks!