popping from exhaust/ valve train noise

[chris71]

ok guys, i just got done putting the headers back on last night, and she is popping out the back of the passenger side exhaust, she used to pop before, at idle, its a nice consistant pop, i know i have an exhaust leak at the collector on the passenger side, i seem to have picked up some valve train noise on the pass. side as well (i did switch from 10w30 to 5w30), and when i took the plugs out to put the headers in i noticed #6 plug had some extra caked on carbon build up on the plug. I have have had a collector leak on the same side before and the popping was there too what does this sound like to you guys,
1).could the collector leak be making the pop out the tail pipe and a loose rocker stud nut be making noise in the valve train
2). could a problem in the valve train be causing the pop and the noise in the train
3). could this be a timing or vacuum leak issue (but if it were would the pop/noise be on both sides of the car?