ML 55 Running rough again
 

Hello all,
I have a 2000 ML 55 AMG, and I am at a loss. I am having issues with a check engine light and poor running. I have already replaced the fuel filter, fuel pump and MAF. Plugs were done less than a year ago. I am at a loss. it runs great for a day or 2, then lots of missing and hesitation then the check engine comes back on. My portable reader can't even read the fault now.

Could it be as simple as the fuel pump relay?

I am at a loss, any insight would be much appreciated.

Thanks,
jason