Ok, this may sound dumb, but I have a really bad Back Fire in all gears wether it's cold or up to temp. I have checked the Wires, they are with in the Resistence it needs, Coil, its where it needs to be, Cap and Rotor nothing odd there. checked the timing, ok. So, Im down to spark plugs, Could the Gap already need to be checked?? I know your supposed to Gap check them before you put them in, But I was in a hurry when I did the ReBuild and just put them in. Now my Chiltons or Haynes isnt specifying a Proper Gap. BTW: 89' 2.6L 4ZE1. and its really loud when it does it only while shifting gears. If anyone has pointers and gap Spec that would be Great. Thanks.