[Mark1]

the cat is the first restriction of conciderable size, but it does not regulate the pressure. There are no specs on flow for cats, just exchange rates. But what you mean i beleave is true as well... the restriction incured with the cat is great enuf to minimize the restriction in the muffler.

For thoes who dont know what we are talking about, think of your exhaust as a fire drill. Remember thoes from grade school?

Every body ( the exhaust gas) is rushing out the classroom door (the cat) it filters the people through 1 at a time this is a restriction. The doors at the end of the hall are double doors (the muffler). They too slow every body down but mabie too 3 at a time, not near as much as the classroom door.

Because the class room door slows every body down so much the double doors never really get backed up enuf to be that big of a restriction, but slow down people just because they are there.

This is why we do not see that big of a performance jump when we add a better flowing muffler.