The last post I covered the inflow, but there is also the out flow to take into consideration. I am talking exhaust.
I am in the market for a new muffler so I asked the mechanic at a muffler shop to check the exhaust system and give me an estimate. Well he came back and found that the muffler and the pipe before it needed to be replaced. Of course I asked for an estimate and he said it would cost me over $700 to fix it properly.
It used to be, that all you needed was a muffler to reduce the noise. Then came the catalytic converter, which reduces the exhaust gases coming out. Both the muffler and catalytic converter are required by law.
Exhaust looks for an easy way out. The easier the better. But the exhaust gases have to content with the catalytic converter and the muffler. Both unfortunately create a restricted flow. This also reduces fuel efficiency.
Now, you can increase the airflow with with a high performance exhaust. They even sell a high performance catalytic converter. Of course, they have their draw backs. You get better fuel economy, but it will sound louder. That's why you don't see mini vans with high performance exhausts. Just imagine arriving at a soccer game sounding like you need a new muffler. They however do sound cool on a souped up Honda Accord coupe...ask any twenty-something.
Another drawback is that like other high performance parts, they are expensive. For my application I am looking at a $1000 installation. The mechanic did say that the metal on high performance lasts longer than a conventional muffler. So it would most likely be the last muffler you buy for your vehicle.
So you gain better gas mileage, more horsepower and longevity. Does this outweigh the higher cost? That's up to you to decide.