Tire Sidewall problems of the 2001 Saturn LS

While driving on a clear level road the left rear tire ruptured at the sidewall for no apparent reason. I also noticed that the vehicle veered heavily to the right under acceleration. I then checked the tire pressure on all four wheels and found them to be normal prior to the tire rupturing. I then returned to the dealer with the tire and explained what had happened. I also complained to the service manager steve about the car veering heavily to the right. I then explained to him that I didn't feel safe with the tires that are on the car and requested that they be replaced with goodyear equivalents. The dealership agreed and replaced the firestone tires with goodyear integrity tires. I was then advised by the service department that they could not duplicate the problem with the vehicle veering heavily to the right under accleration and that nothing had been done to the vehicle other than replace the tires. Since replacement of the tires the vehicle has performed well without the veering to the right. I noticed that the rental vehicle had the same firestone tire and found the sidewalls to be soft. This after checking that the air pressure had been normal. Please investigate and advise. (tiresize: 205/65r15)( dot number: tire size: 205/65r15 ).