An engine is a giant vacuum pump...
The other day my grandson who is working on four years old asked me "what is a catalytic convertor" and he turned his toy car over and showed me it's exhaust. Don't ask me where that came from, but he wanted an answer so he got one. I explained that his car's engine breathed and we looked at the engine and I told him it breathed in through here and just like him when he breathed in it had to come back out. And then a very glossed over explanation of a Cat.
Thing is though, the exhaust side of your engine is as important as the intake side and in some ways more complicated. Take a look at a McLaren F1 exhaust system sometime and understand that the computer program written to design it is way beyond most of us to understand. To much exhaust can be bad but then so can to little.
We are Hooker, Flowtech and Magnaflow exhaust dealers and have access to many other exhaust systems. Let us help you get the correct system to maximize your car's "breathing" and make sure it is installed correctly