Do you mean the spark plugs, or other plugs? It only recently had Cylinder 1 missfire before doing Cranksensor, then yesterday it was missfiring on two cylinders, took coil pack off to check for oil, etc. nothing in the wells. When I put the pack back on, it seemed to be rocking if pressed on each end, if that makes sense but once the two torx bolts were torqued down the pack had no rocking at all. The Previous Owner had changed the plugs and coil pack, due to a missfire problem he said it seemed to have cured it, also the engine has recently had a top end rebuild done, it was in the paperwork which came with the car. I drove it all the way from Darlington to Scotland with no missfires, the engine ran perfect. I had gearbox codes so changed the Camshaft Sensor and put in a new Battery as the one on it was going, cleaned the terminals at the same time. The gearbox has been fine since, just kept getting a camshaft code, so on advice from here I changed the Crankshaft sensor. Now getting missfire codes. And car shudders as if it running only on a couple of cylinders. But as said went to it this morning and started and moved no problem. I am hoping to put the new spark plugs I got for it, in today.