Yeah most likely not the coil. Check the coil sleeve, clean or replace it. I would also pull out the arm/linkage assembly and clean it. Mine had old grease on it that had gummed up.
Also, if you think the ball may be getting slowed down by hitting the post on the right where the shooter lane news the plunger lane, put a smaller rubber ring on it. And the alignment of the kicker to the ball is very important. Sometimes you have to play with that by adding washers to the mounting part.