Exhaust: Do we really need back pressure?

[Cory_Langford at bcit.ca (Cory Langford)]

Just finalizing the exhaust set-up and I was wondering what the opinion was
on running a completely free flow exhaust.

One of the tracks has a noise restriction, and one does not.  So I figured
the simplest design was from the header to 2.5 inch pipe straight back (no
cat, res. etc).  I figured I would have a removable muffler that can slide
in when needed, and a straight pipe when not.

But I have seen some talk on the vw engines needing some back pressure to
keep the exhaust gasses hot enough to travel quickly through to the end.
So I was wondering if a simple straight pipe would have any down sides to
it (beside noise)?

Cory