Spark Plugs, Engine Shake??

[Hitman73]

I took all the plugs out and well need some assistance- plugs 1-4 were fine and had normal wear, plugs 5-8 a different story plug #5 had carbon fouled, plug# 6 normal wear, plug#7 Bad oil fouled, plug#8 bad oil fouled both 7-8 were pretty bad and i replaced all but what is the problem on my 5-8 side of the block?.

Then as i started it up after plug change the engine was shaking pretty bad i then turned up idle a bit and it stopped shaking so bad like before but the idle was so high it wants to keep running after shutoff. I then backed off idle enough to stop that but it still shakes some is that ok whats up with the shakes ?.