Just guessing but it may have nothing to do with the plugs at all. Often while changing the plugs the fuel lines get messed up. The very fragile fuel lines brought to you by the finest German engineering money can buy.

Does it clear up and run well after a while? If so, do you have an incline on which you can park it overnight? If so, fill the tank and park nose low for the night. If it starts right up I think you found the problem. You may also look for small fuel leaks that would otherwise let air in. Good luck.