[american-kiwi]

did you look at the numbers-to plugs on the cap "before" you pulled the wires?...PO might of had the dizzy pulled and timed at a diff' setting...re: cyl-1 becomes cyl-8 or cyl-3 etc...or did you bump the dizzy...and throw the timing out?...but like Danglerb says...sounds like a vac' hose could be off somewhere...runs fine at idle...them backfires under load...throwing the timing out with no vac-advance...John