There are only a few air paths into the front chamber past orings that could cause a valve to go full auto. They are the on-off top, the reg valve seat, the reg valve pin back orings, and the reg valve front pair of orings. You changed the on-off, so that one shouldn't be the problem. You changed the reg pin orings. The front valve pin orings shouldn't be the issue or you would be getting air venting out the hole in the top of the valve. Make sure there isn't an extra oring stuck in the on-off area.
Check your sear. If the issue isn't oring related, then it could be a worn sear. What rail are you using? If it is an automag rail, check that the sear pin is fully pressed into the recess.
Except for the Automag in front, its usually the man behind the equipment that counts.