Vacume Problem?

nope, It didn't matter where I had the Dist set. even if I had it turned all the way to the left, or the right, and everything in between, it allways backfired. Without the vac adv, it runs perfect.

My timing gun kinda worked today, and I got it at 10*. it still runs bad with the vac adv hooked up, but mint with it pluged.