My 2013 VW Golf TSI isnt running properly, jumpy, stalling. Mechanic says that tip of spark plug has broken off and fallen into cylander leading to multiple misfires and he can’t assess scale of damage without taking off cylander head (3-4 hours labour minimum) Says best case scenario he’ll have to replace part of engine if not whole thing given likely damage caused by broken part flying around while engines been running. Sounds bad, any advice?