Congrats on using the best 4bbl, the TQ!!
[1] Lean backfire could be sec jets too small OR pri jets too small. It just depends where exactly in the pedal movement/rpm you get the backfire. Try going to about 3/4 throttle [ not full WOT ]. If no backfire, probably needs bigger sec jets.
[2] To richen the secs overall, tighten the AV. Go to about 2.5-3 turns. You do not need a special tool [ sure helps! ], just the right size screwdriver.
[3] Ign timing. So much confusion about this. At cruise, with the centri adv inside the dist fully deployed, total timing can be 45-55* & sometimes as much as 60*. This is comprised of initial + centri + vac adv. Is the VA manifold or ported sourced? When you go to WOT, VA goes to zero.
