1998 Clk 320 AMG 57000miles always MB serviced. Had to change battery other day, since changing car gets upto around 4000 revs then starts pulling back and want change up to fith gear, if i gently acellorate it does go up into fith.
Thanks,

 

My C320 V6 had a similar problem once and I was told the vehicle goes into limp mode to protect itself but get you to safety/dealer. I suggest having the fault codes checked as a starting point, maybe the changing of battery left a surge/spark to cause damage to oxygen sensors or the likes. Good luck.