engine miss

I just purchase a 1979 kz1000 st. The bike looks almost too good. It runs however when I put the choke on to warm it up it has a miss or almost a spit sound comming out of the exhaust. As it warms up it is less noticeable but still present. I also hear a noisy rattle in the airbox when it is at idle, is this normal?? (I have the airbox cover off and the seat up)

Any help would be usefull, a newbie to the bike scene!!