We haven't heard any pinging, knocking, rattling at all. But then, we haven't driven it for any longer than 10 min. We just got it about a month ago and have been busy modding it. Dude that gave it to us didn't mention anything about engine noise, and he would have as he's paranoid about noises after he blew the engine in his Cherokee. (We rebuilt it for him and he gave us MJ in trade).
But, we'll definitely get that replaced! Thanks!