Rough idle after changing knock sensor


Test Drive
I changed knock sensor, new valve cover gaskets, new intake gaskets, everything seemed good except I have 4 round spacers left. Haha didn't seem like they needed to go anywhere I installed 4 have 4 left...anyways got it running everything seemed fine bled the cooling system ran for about an hour started it this morning -8 Celsius and it was fine on start up came out 15 min later and running like crap and continues to at idle driving is fine lots of power no stalling or hesitation...wondering where I should check. Spark plug wires? Or possibly fuel injector issues now?