If your a Mechanic you dont just replace thing test them. check your plugs first make sure the gapping is right. then check to make sure the leads have the right restance in them, and finally look for signs of arcing on the coil area and the dizzy you will see some discolouring happing. checks for cracks aswell.

Mechanics arent just ment to be replacers there ment to fix the problem if it can, Not just reaplce everything.