Backfire issue

3.0L OHV. I just replace the intake gasket and valve cover gaskets. I did have to remove the push-rods in order to remove the intake and gaskets. I turned the motor to TDC on each cylinder before loosening the rockers just enough to get the push-rods out. I did not remove any rockers and I kept all the push-rods with their original valves.

After replacing the gaskets I reinstalled the push-rods one at a time with each cylinder at TDC and torqued the bolts down to 24ft lbs. I turned the motor over a few times by hand and everything seemed to be moving well and correctly.

After everything was put back together I fired it up, it started right up but immediately it started to backfire (it's all electronic timing so I know that's not the issue). After pulling the plenum and rear valve cover (where noise was most noticeable) I discovered the number two cylinders intake valve was not closing completely. Even at TDC the rocker arm is still applying pressure to the spring keeping it slightly cracked open. It is the only cylinder with this issue. I inspected the push-rod and rocker, both are fine, the lifter moves up and down smoothly.

Where might I have gone wrong, or is there something I'm not seeing? It wasn't doing this before I changed the gaskets but I can't figure out where I messed up. Help would be much appreciated. Thank you