I would check the gap. I usually find the gap is either large or small depending ont he plugs.
I always check my gaps before I install the plugs. I also check the gap according tot he old plugs too to see if there are any discrepencies in the gaps.
I would set the gap to factory specs for the gap.
The plugs you buy can probably be use din other cars, so my thinking is the gap may or may not be correct for your car.
'92 300CE - Sold
2004 C240 - C7 Wheels
2015 ML350 - P1, Pano, Ash poplar wood, Sport Dinamica interior, Running Boards Keyless go.