various responses about no muffler

About a year ago i took my muffler off my eclipse and come to find it sounded pretty good well my dad heard and hes a mechanic he told me that over time you could totally screw up your intake and exhaust valves. Well i told my autotech teacher and hes ASE certified and what not he said it might it depends on the car. I really need some help on this one. Should i straight pipe it and get rid of the muffler or should I buy one a muffler and put it on. But my car does sound good without the muffler.

My understanding is that it depends if it is a turbo or not. I know that the best exhaust for a turbo is no exhaust at all. The free flowing exhaust, or lack thereof, allows to turbo to spin without any backpressure. I think with an N/A that the engine requires some backpressure. So it would seem that it wouldn't matter on a turbo, but I'm not sure what car you have.
Can anyone back me up on this?

:gay: dude get a straight pipe, and a full 3" catback with downpipe/header

with no muffler on an NA you're giving up alot of low end torque for a very little bit of top end hp.

No motor ever needs backpressure. Search backpressure and velocity using my user name, and you'll find some answers. The valves will be fine too.