We’ve done a few of these Porsche back box mods now. I’m told the top performance cars use the same boxes but have a bypass pipe which drop the back boxes internal pressure into the tail pipe, so increasing flow whilst still keeping some level of sound control.

The first one we did we modified the customers existing boxes based on some pictures he had and it all looked like a perfectly plausable modification. The next one was a chap who’d purchased what he believed to be the same thing from Ebay in Germany. When we opened the boxes we found the exhaust had been modifiied in a very differnt way. It looked as though someone had welded a piece of old stool leg straight between the inlet and outlet of the exhaust totally bypassing the box. The quality of both the metal and the welding was pretty dubious.

We informed the customer but he wanted them fitting anyway which we duly did. To be honest the exhaust still sounded good when the car was running and the customer was happy which was the main thing. I think it’s lucky he couldn’t see what his exhausts looked like though and he wasn’t concerned with the performance implications. It just goes to show you need to be careful what you buy off ebay and what lurks beneath your car as a good exhaust is more than just the noise it makes.