I own a 98 slk 230, lately it has hesitated when trying to increase speed. it seems like it is going to back fire. I thought it might be the humid weather. I changed a mass air flow meter around 6months ago. I put some fuel injector cleaner in it. and just ordered new spark plugs. the ones in it are only a year old. so I am not sure what it is that is causing the power loss when flooring the gas. could it be a fuel filter or computer problem?