I have a 2007 Grand Touring 6 speed auto (yes, I know) with 94,000 miles on it that I picked up in December of 2014.

My engine is so quiet that the first time I brought it to the dealer to have it checked out the mechanic tried to start the car (squealing the starter motor) because the car was already running!

So if you think you have a tappet like noise I'd bring it to a club meet and compare it to other cars that are stock, or take it to a dealer and get an opinion.