I know this sounds like a stupid question to some of you guys out there but here goes. I recently bought an EXT 600 when I start it up it sounds louder and better than my 99 ZRT 600. It has cylinder heads that have ZRT stamped on them and three separate pipes that terminate into one box. The dealer told me that someones (only on sundays ;>) wife rode this thing I am wondering if she was related to "shirley Muldowney" the way this thing sounds and rides.....What do you guys think?
Just learning the ropes

Those motors had ZRT on the cylinders because that is a ZRT motor. They had triple pipes into one box and they were loud.

Is there any kind of stamping on the pipes or silencer indicating after market stuff? Do you have a pic of the engine compartment you could post in here so we can get a good look at it? Do you check for exhuast leaks from the pipes or seals that's maybe why it's loud?

Being it dumps into a box, my guess is it's stock. My '96 is stock and it really raps, especially on a garage floor. My guess is by the time your '99 was built, Cat quieted down the beast a little (and also took some power with it).

Yepper, about 7 hp, but if you were able to fit it with 96 pipes you'd be back at 125hp.