manifold vaccum for vaccum advance ?'s

ok guys, i ot some interesting news for you. For all of you guys who said the thudding out my exhaust while at an idle was a (miss) you were dead on accurate!!
I remember somone on here saying a (miss) could cause the smokin out the exhaust while backing off the throttle from higher rpm's. So last night i was in my shop tinkering with the engine, ever since i had put my vaccum advance hose on ported vaccum i didnt like it and could not get it to run nearly as good compared to with the vaccum advance on manifold vaccum. So i re-adjusted my vaccum advance canister to add 10 degrees of timing at 18 inches of vaccum. Then i plugged the vaccum advance hose back into manifold vaccum and fired it up and listened and sure enought the thudding out the exhaust was still there. So i pulled the number 5 spark plug, because the number 5 plug was the one that was black and i had guessed that i had a leaking intake valve seal. So just for the heck of it i grabbed another plug that i had laying around thats brand new only been ran thru my engine once. And the extra set of plugs that i have are bosch platinum fusions. Anyway i put one of the bosch platinum fusion plugs in the number 5 cylinder and fired it up and holy cow!!! night and day difference in the idle and in the throttle response and in the way it sounded. I took it out for a drive and the acceleration was way smoother then before!!
So i get back home from my little cruise after putting the bosch plug in the number 5 cylinder and i sat back and listened to the exhaust for 5 minutes and i couldnt hear anymore thudding out the exhaust.
After not hearing the thudding anymore i decided to throw my vaccum gauge on it to see what the vaccum reading would be and i it would be more steady, and sure enough vaccum stayed between 17.5 to 18inch and it hardly moves at all, for the most part the vaccum is very steady and if it does move it might go down to 17.5 to 17.8 inches and thats it. But before with the vaccum gauge on it the needle would drop down below 17 inches of vaccum and then back up to 18 inches then back down and then back up very unsteady vaccum. But now the vaccum is alot more steady like night and day difference. Can a bad spark plug cause unstable vaccum? I'm thinking it can because ever since i replaced the number 5 cylinder plug the vaccum is steady and no more thudding out the exhaust at an idle.
Now the reason i had such a hard time believing i could have had a (miss) is because my distributer is brand new curved and phased at fbo systems i have a brand new standard blue streak cap and rotor my plug wires are brand new borg warner selects and my ignition module is a brand new 4 pin Wells module and all my wiring is brand new. And my ignition module is grounded to the engine block and so is my voltage regulator. And the spark plugs i bought brand new about 9 months ago and they are the NGK zrf511's and they dont even have 1000 miles on them yet. So it was real hard hard for me to believe there was a miss because viryually all of my ignition parts were brand new with hardly any miles on them.... so i started doing some re-searching online about plugs just up and quit working, and i found that it can and does happen quite a bit, not only did i read that, but alot of people have reported having NGk plugs that just up and stopped working, i saw more complaints about ngk plugs that up and stopped working over any other plug.
No my last and most important question, The smoking after i back off the throttle from higher rpm's, i took it out after realizing the ngk plug had took a dump and stopped working and i ripped around and got on it pretty good and backed off the throttle to see if it would still smoke out the exhaust and it did, but there wasnt as much smoke as there was previously with the bad plug in the number 5 cylinder. My question is, is it possible that with the number 5 plug being bad for who knows how long now, is it possible there is alot of un burnt fuel and oil on the number 5 cylinder that will need some time to burn off? Just wondering if maybe over time the excess fuel and oil that got into the number 5 cylinder cause of the bad plug will burn away and the engine will stop smoking after letting the throttle from higher rpm's, is that a possibility? Because somone on here said a MISS will cause smoking out the exhaust while backing off the throttle from higher rpm's.
I purchased new intake valve seals and exhaust valve seals and i have a friend with a good air compressor and the valve spring tool and he said one of these weekends when he isnt busy he will call me and i can take it to his shop at his house and that he would help me change them out. I just dont wanna have to do all that work if its possible the smoking will go away now that i have a good working plug on the number 5 cylinder. And just wondering if its possible that there is un-burnt fueel and oil settled in the number 5 cylinder because of the bad plug and thats why i am seeing the smoke after backing off the throttle at higher rpm's. Remember my compression test checked out good every cylinder had between 145 to 150 psi.
Sorry for such a long story, just wanted to tell the guys who were telling me this is a miss that they were right and ask about the smoking issue and ask if its possible that this smoking issue may go away now that there is a good working plug on the number 5 cylinder.
I have 8 of the bosch platinum fusion plugs and i ordered another NGK from the parts house that will be here thursday. But i'm not sure i wanna run the ngk anymore because this issue caused me a big headache and all it came out to be was a 2 dollar spark PLUG!!! so would i be better off just to run all 8 of the new bosch platinum fusions? or should i give the ngk's a second shot and just run the bosch in the number 5 cylinder untill the new ngk gets hee on thursday?