The bulk of the problems started with the 2005 production year. As mentioned, there is no factory warranty. Even if the seller or dealer gave you a warranty it would be for a short time and most likely before you have a problem.
Who are you buying the motor from?. If a dealer, ask them to state the condition as they see it in writing. They may not know about problems, but if they do, they legally can't lie.
Of course proving that later on is not a simple task.
Regardless, have the exhaust scoped, preferably by someone other than the seller ( Having it done by the dealer is OK as long as they will put the results of the scoping in writing.