Coil Pack #2

Just got a 99 Merc. C-280 it came with no manual, changed the spark plugs, to give it a tune up, it is still sluggish, got it checked, coil pack #2 bad, if I am looking down at the engine where would coil pack #2 be located, also could it be possible that if the codes were not properly cleared out, can the computer cause the same problem, and or if  the CEU is bad can it effect one or more coil packs, or would a DIO identify that the computer is bad.

Thanks to all who can help with this….