everybody is telling you the right thing!!! we run 7s on our cars and we set on at 28, whe we got to the track we take out the plugs and regapon they open up with the high hit at high rpm, so fron time to time taken them out and regapon

 

yea plugs look good, could just be too big of a gap on the plugs and the spark blowing out on top end, or could have just been you hitting the redline (fuel cut)
that will sound like a 2 step or aka explosions at times
as long as you keep the bkr7e in there and gap them to about .30-.28 you should be fine. Just make sure your not burning anything off, like oil or coolant.