Probably. I used to own an IH Scout with a turbo diesel that was straight-piped. I once met up with a guy who had a naturaly-aspirated version of the same engine, and was properly muffled. My truck was quieter, by a fair margin!

I don't plan on modifying the exhaust on my 123 just for the heck of it, but if I ever need to replace it, I'll just go for a straight exhaust...no harm and may even pick up a horsepower or two