5.2 magnum options

ok, thanks to the rain & cold I had a few minutes to mess with the car last night.
I pulled the dist. to install a advance limiter I had and to check it over. I found the roll pin for locking the pickup plate and vacuum advance missing.
this cant be helping the rotor phasing or the ignition in general. so thinking I may have found the problem I buttoned it back up and started it up.
no Dice, still missing same erratic miss as before. I tried to isolate one cylinder by pulling the wires one at a time off the dist. cap. zero difference between cylinders.
now I am really puzzled. compression test was even on all cylinders, pulling the wires doesn't identify any one cylinder. yet the engine has a noticeable shake at idle, you can hear it in the exhaust. I guess next is to pull the push rods and check for bent ones? look for broken valve springs?