Hi just got my first toyo pickup its an 86' that had a motor with rod knock so i ended up coming across an engine that was built. Its suppose to be bored over with high comp pistons, cam, head work, weber carb, 20r intake. Well all that sounded great so i bought it. had it in and running in a few days but however everytime i try to accelerate hard it back fires through the intake? Im running stock headers which i was tould it needed aftermarket ones or it would burn the valves up? also what should the timing be set at? any help would be great right now. thanks