Hi I have a 2015 Mercedes c400. The problem is I have a check engine light saying I have a misfire on all 6 cylinders. The car was running fine no problems then I get a stage 1 tune and the car runs fine see no problems although a check engine light came on saying it's misfiring at all cylinders.
Is the tune the problem ?
or it's possible that I just need new spark plugs for all cylinders ?

Who tuned it, AMR?

P0300 code? or are you getting a P0301-306 codes?
how many miles on the plugs? interval is 46k and its recommended to stick with that, especially if tuned.

I have 84k right now, and the code des not sure when it was checked they just told me it was saying it's misfiring in all 6 although car runs fine.

E tuners Motorsport tuned the car