Mercedes Benz South Africa - Unhappy Client

I purchased a Mercedes Benz CLS63 AMG S second hand from a dealer in Witbank. Once the vehicle was purchased I experienced a slight noise in the suspension. I immediately took the vehicle to an accredited Mercedes Benz dealership namely McCarthy Kunene Witbank in order for them to thoroughly go through the vehicle so that we could establish what the problem was. Once the problem was diagnosed McCarthy Kunene informed me that the vehicles warranty & motor plan had been terminated previously due to the fact that the Catalytic Convertors were removed by the previous owner. I was forced to pay in order to have the suspension problem rectified due to the fact that the vehicle was sold to me with no warranty. I immediately asked McCarthy Kunene how we could go about reinstating the warranty and the motor plan, McCarthy Kunene said that they would contact the warranty / technical department at Mercedes Benz South Africa and get back to me ASAP. A couple of days later they informed me that the warranty can be reinstated provided that McCarthy Kunene Witbank replace the original exhaust system as well as carry out a 72 point check on the vehicle. I immediately contacted the dealership where I purchased the vehicle from and asked them to supply me with the vehicles original exhaust, when I received the exhaust system back I immediately went to McCarthy Kunene where they replaced the original exhaust system and carried out the 72 point check as per Mercedes Benz South Africa. Now after all of this and me following their instructions 100% to the book, they have now informed me that Mercedes Benz South Africa are no longer willing to accept this in order to reinstate the warranty and that I should purchase a brand new exhaust system which costs in excess of R100 000-00 in order to reinstate the warranty. I feel that this is totally unacceptable as I have carried out everything according to their specifications and I cannot afford to pay in excess of R100 000-00 in order to have a warranty re-instated. The vehicle is back to its standard form and has been checked by McCarthy Kunene themselves. What can I do in order to resolve this as a matter of urgency?