misfire on 4.6 dohc

i have a 96 lincoln continental w/ 4.6 dohc.misfiring with no codes. i get a misfire count on 4 and 6 and eventually 8 and sometimes 1. found rusty gas tank..replaced gas tank,pump,plug wires,plugs,coils,egr,cam sensor,fuel regulator.cleaned the injectors. still running the same. once its over 2000 rpm it seems ok..also vacuum is a steady 20 at idle.....2 and 4 plugs seems to wet with fuel. i swapped injectors.still the same