aside from the tips, can u visually tell if a car has the Porsche Sport Exhaust installed? By looking underneath does the exhaust look different from the stock version?

 

If you really look underneath you might see the actual vacuum assisted valves and the lines going to them. Under the hood you'll see the vacuum solenoid and all the vacuum lines and harness connected to it.

BTW: The PSE exhaust tips really have two inlet (2) ports from the PSE mufflers unlike the standard 'S' tip that is really just a fake.

 

Switch on the dash if it was factory installed.