The first run K you bought.
Any prollems?
Are you running the crap out of it?
Be truthful. 
I have one also. It has QSI sound. Love the loco but it won’t navigate the R3 curves in the train room so it doesn’t get run a lot. I have had no problems with the chuff but I’m not knowledgable enought to give a real opinion. I have recurring probleon but I find them along the the track at times??ms with the front cylinder caps coming off. They sanp
Ive only run mine on track power on about 15 feet of flex laid in the family room. Runs nice that way. The tender is now apart and half gutted, for installation of RCS and sound. Its about half done, or so. With another 14" of snow this weekend, the railroad is buried until April!