Sorry to have come to the thread rather late.
The first thing I would want to ensure is the op rod is not being pushed off center by the scope mount over the barrel. It probably isn't, but I would check that first.
When I was a standard MOS 2111 Infantry Weapons Repairman/Armorer and we worked on real G.I. M14's, we did not worry about where the op rod aligned on the gas cylinder as long as the op rod slid freely in it's track and the rifle functioned properly. Most op rods did not align perfectly to the pistons.
As a MOS 2112 Rifle Team Equipment Repairman/ NM Armorer, we glued all the op rod guides so the front of the op rod would align as close to center of the op rod front to the gas piston side to side, but not up and down. You can't adjust where the op rod will hit the piston up and down. We did that for accuracy of the rifle loading the round and that does help accuracy of the rifle. How much? Depends on the rifle to be honest. I don't even have a clue how much better accuracy you would get if the only thing you did was properly align and glue the op rod guide as we never tested that modification all by itself.
If you want to see if your rifle will shoot better, use Federal's American Eagle ammo or Winchester's white box with red Winchester letters and all other letters are black. These are loads that are meant to be used in military type gas guns.