[boxhead]

Wazza,
You forgot some of the Cons of the under car system
1= to fit the system under the car I am guessing they will be under the chassis, so to have a decent size set of pipes your car will need to be pretty high to gain gound clearance to be both legal or practical (since the car will be used every day you will not wanting to be going out of your way to avoid speed humps).

2= with a Cobra that high of the ground it will not be as pleasing to the eye as it could be.

3= you say it is to be used as a daily driver, but then mention on a high horsepower engine where your chasing every last drop of power it could make a 40hp difference, do you really want an engine that is "on the edge" so to speak in a daily driver?

But then I suppose being in a State where legal side pipes are not an option then you really have very little choice if you want to stay out of Mr Plod's vision.

This is all just my opinion and the reason for side pipes on my car is that part of being a Cobra is having the live side pipes.