The issues people have had with CO poisoning are real, but it's not every person, every time. My understanding is that it's more about the people in the boat, especially toward the stern. But the air current over the boat in calm weather tends to collect exhaust gases (carbon monoxide in particular) in the area where people sit. Prolonged exposure, not good. 

Lots of factors contribute to whether you might get sick, including the wind speed and direction at the time, and of course how long you spend actually riding. 

If you want to do it a lot, I'd get a FAE, no hesitation. But that's me. I don't have one, we don't surf much. I suspect people on the other Nautique site will have some opinions about this, too, and I doubt a lot of people will tell you not to worry about it. It's not because of the noise that "surf boats" all have these installed...