looking toimprove my exhaust

so I got some Jardine rumblers slash cut one sided two pipe after market slip ons. and I'm having trouble with them staying on nice and snug, but luckily the pip goes being my battery box which keeps the pipes from sliding off, also I would like the exhaust to sound better and the baffles are removable, so any recommendations on the sound issue? I am looking for a solid deep throaty sound! rite now it sounds like a lawn mower haha, mind you I do have some exhaust cement . but my main issue is  my spark plug holes, I was cleaning it out gunk in the wholes and I lost a couple small pieces of paper towel. I should be ok rite?? also how can I clean the plug holes out thoroughly because there is stuff on the bottom that I don't like, and one last thing, why would only one of my plugs look so much black and greasy? thankS a lot everyone