I bought this muffler to replace the stock muffler and hooked it up directly to the stock pipe. I love this silencer. It's relatively small, meaning it can easily fit under a car. It weighs less than I expected. I also like that it's not very loud, but I've definitely noticed more throttle response, turbo boost, and even a slight increase in power. This is because it is a pass-through construction, but noise pollution has also been taken into account. I have a 2004 Jetta TDI so it fitted my desired setup perfectly.