Callas Rennsport was awesome! They replaced my stock muffler on BMW M440i with a Dinan Exhaust. It was more difficult to install than the Dinan instructions, it took more than double the amount of time to install and they did not raise their estimated quote. Tony the owner was awesome, he was hands-on making sure all bolts and placement were accurate. Eddie and David kept me updated on the install, everyone was very professional, I highly recommend them for any BMW work needed. Car sounds amazing. Thank you again!!!