So I recently got a FI Vacumn Valve (bought from Golan @ AutoTalent) exhaust installed on my C63s Sedan. For the last two months its felt different like it doesnt accelerate as aggressively from standstill anymore. I took it to the dealership last week and sure enough the tech who also owns a c63s immediately said the car feels like its holding back. He took the exhaust off and drove the car without it and it feels like it used to before. Also, he checked the temperature of the two sides of the tail pipe and the drivers side is about 40 degrees hotter compared to passenger. Also, he said, there isn't enough flow coming thru the exhaust like something is blocking. I know this exhuast system has an X-pipe versus the stock H-pipe. Could this be the issue? Anyone have inexperience with this kind of exhaust?

You need either a tune to delete it or have a valve simulator for the middle / any other valves. Dealership wont be able to see the fault code. We've done a car that runs great with the same exhaust. Owner did end up doing down pipes because it was quieter than the stock mufflers. Contact Modern Mercedes Repair Specialists they are in Dallas.

Oh ok that makes sense. You said “we” so does that mean you work at modern Mercedes repair? Either way I’ll contact them to see it they can help. Apart from that issue, how did your client like the FI exhaust. I personally don’t think it’s worth it. Should have gone AWE switch path or something else.