Two questions:
1, Does it smell like sulfur or eggs? 2, What type of gas do you get?
I used to get a sulfurish smell when I was driving at high RPMs along with a most delightful pinging sound. I switched to a higher octance gas (92) and the sound and smell seemed to go away. Might give that a shot if you want to spend the extra 20 cents a gallon at the pump. Just my 2 cents...or should I say 20 cents?