i noticed my auto 98se with 30K on it is making an ever so slight ping/rattle. it only occurs when I give it a moderate amount of gas while in a high gear, the moment before it kicks down a gear. once it kicks down a gear and the revs climb it runs great. i am using 91 octane. like i said, the sound is very slight. is this normal?

 

Slight and occasional pinging such as you report is acceptable.