Be careful buying a modded truck.I've seen to many people have issues. You could find a stock truck and do the deletes yourself. You can still find the deleting programmers on craigslist or ebay.then you know what you got.just my opinion of course. Good luck.

take a long test drive

on the 6.7s make sure the over flow tank is at normal fill. drive it around get it good and warm make sure she dont puke any out if so head gasket issue. also gurgling sounds coming from the over flow tank