I have suffered a great deal of pain around my rib cage driving my 17 volt with cloth seats. I too have never had this type of problem with a car before. I got some good advice from the forum here about getting cushions to try and alleviate the problem. I got a backbone support cushion from amazon which i have installed under a general car seat cushion. The bigger cushion has been effective with the side edges to the seats both along the rear and the back which were too small and sticking into my body. I am 5'9, 185 lbs. However, after about 3 weeks the rib pain has not gone away although its a bit better. At first i thought the cloth seats were to blame and considered changing the driver's seat out for leather or for another GM seat. However, now I think that its a combination of the position of the steering wheel and the seat and the alignment of the driver in the cockpit. I noticed that if i move the steering wheel around the location of the pain shifts slightly and becomes more or less acute. I believe that the steering wheel is positioned too low and too close to the driver who is also seated too low in the car. This causes the chest muscles along the rib cage to become isolated and strained as the steering wheel is turned. Although I am reasonably fit my chest is constantly hurting and am at a loss right now as to what to do about it. Maybe changing out the seat would help but I am no longer very convinced this is a solution. I hope this helps.