Maybe the previous owner did something to the exhaust also?
Never noticed any exhaust ticking on mine at anytime I've had it. I do know that the A/C condensate does drip on the exhaust but never did notice any noise from it.
I have had alot of comments from people saying they didn't notice it was a diesel due to how quiet it is. It does have a little growl if you're getting on it, as it should, but nothing I'd consider loud.
Really like how it tows. Has no problem getting up to speed and cruises really easy. Buddy of mine has the 6.6 diesel and tried mine out was impressed how well it does and the mpg to go with it.
Hope you get a chance to test drive a unmolested 3.0l truck to have a better perspective of it.
Planned on going with 6.2 in the beginning of my truck search, just for the fun factor, but after seeing the reports on the 3.0l and then getting to test drive one decided I had to have it and haven't had any regrets from long trips to towing or regular usage. Fits what I use it for very well!
Good luck in your search no matter what you decide
-Grover67