Do you run a Cetane booster?
I've been reading that these cars are designed to run best with 50 cetane fuel. Unfortunately I can't find anything even remotely close to that here. Nothing even has the cetane rating on the pump and there are no "premium" diesel pumps. Based off what I've read that means they are closer to the minimum rating of 40.
After filling up at my local Shell station I believe it too as the car seemed noticeably louder after just a few miles. I bought some redline cetane booster and dumped in about 6oz. They claim this can raise the rating by 7 points. It must have done something because it seemed to quiet the car down considerably in a short amount of time.
So what if anything are you guys adding to your fuel?