2000 grand am rough idle

Need help please!!!! I have a 2000 grand am 3.4 l v-6 that had a leak in the reservoir ran hot which lead to taking the heads to get machined and new head gaskets...... Put everything back together tried to start it up .. Backfiring and car wouldnt idle... Checked all plugs and wires tore motor back down to check the rocker arms and pins for correct placement replaced one rocker arm... Put motor back together same thing... So playing around under the hood checking for vaccum leaks and un plugging and plugging back up sensors to check for ne difference i notice that when i take the egr valve or oil cap off car idles... Would this mean the egr valve is shot? Also rented a scanner just one code, random misfires ????? This car has neevr given ne problems until it ran hot besides starting issues which i was told in the beginning was the fuel pump it would always start but on the second try so never worried bout it... It worked so didnt fix it. But until this proble starting to think maybe a piston ring after a compresstion check on the cyclinders no compression from the # 2 at all and all others about 170 psi so there you have it ..... Ne suggestions or fixes will help about out of ideas myslef thanks in advance!

this is my suggestion:

- first inspect all spark plug wires to make sure you connected them to the right cylinders

- if spark plugs are OK, remove upper plenum to access injectors: make sure that injector's connectors are connected to appropriate injectors.

- if injectors are connected correctly, remove the lower intake manifold and inspect rocker arm's push rods: remember there are two lengths for intake and exhaust push rods, and if you installed them wrong valve timing will be incorrect with chances of bending valves and damaging top of the piston.

according to the compression test for no2 cyl. I would say valves are not closing when they need to so check push rod positions for no2 cyl remember longer and shorter.

when i first put the car back together i did have 2 of the pushrods in the wrong place and it bent one of the rods so i replaced it with a new one but that was on the number 4 cylinder not the number 2 hich is the one i have no compression on is it possible that when the car blew the head gasket and the water hit the piston it blew out the piston ring

checked all pushrods they r in the right place spark plugs r ok and i am getting fuel still only runs when i pull the pcv valve off the machine shop sayed they shaved 0.125 off the heads is it possible they took off to much? i have no visible leaks of any kind that i can see or hear

o and is there a difference in the front head and the rear head meaning if i were to have put them on backwards would that cause the issues i am having with the car

thanks for thelp 3100 turned out to be a bent valve replaced the valve and car is running fine now

good job, also did you try rolling your push rods on the flat surface or table, to check that they are not bent?