Rough idle + slight Rpm drop then rise to normal at stop lights
 

My 8 has had a rough idle for quite some time. I changed the plugs, plug wires, and coils but still rough idle. It does start better though except for when my battery sounds weak it sometime it naturally doesn't start as good (need a new one). I can't find the problem to the misfire. I cleaned the ESS and MAF sensors but there wasn't any improvement in how it ran. Could it be the fuel pump? I do notice a tapping noise that seems to come from the intake manifold or right below it but only when its at idle. Lifter maybe?
As for the rpm drop, i will sometimes pull up to a stop light or stop sign or whatever it may be and i notice that when my car goes back to idling, it will idle normal for a few seconds then drop just a tad and then go back to normal. it most often does this when i drive at higher rev then stop at the light. Air fuel ratio issue maybe? idk.
Any advice? Thanks

Possible of low compression, try decarb and see if it helps.

Okay i will next time i go back to my hometown. i live in the middle of nowhere there. Too much smoke for here. I havent done it before though. Basically inject about 1.5 shot glasses or a little more of seafoam into each rotor housing separately, let it sit for an hour or two, then crank it up without letting it stall and burn it all out right? It doesnt seem like low compression though. It seems responsive and sometimes it will start up as soon as i turn the key. No different with the engine warm either. Its had misfires ever since i've had it but no major problems (knock on wood). i just cant figure out what it is. i have a new cat to put on it cause the one thats on it is punched out and i want to get rid of the CEL im getting because of it but idt that would have anything to do with the misfires though. It does look like the last owner put on a aftermarket o2 sensor so that could be no good. would a bad o2 sensor cause misfire?
I was told that the ssv could be what the tapping is coming from but i listened to some videos on youtube about the ssv and they were way louder and tapping a lot faster. Mine goes Tap-tap-tap-tap but in the videos it was taptaptaptap. Idk :'(