BTW Firepower is maybe the best pre High Speed SS game.

IMHO you need to reach the fire lanes from both flippers but the right flipper is most important to most game strategies, if you can hit the top lock with your right flipper, I would just buy a rebuild kit and call myself lucky. If you can hit the fire lanes from both, you are getting there.

Here is what I would do.... your mileage may vary.

1) remove flipper coils and see if you can remove and replace the flipper tubing sleeve. If you cant and removing the coils doesn't bother you get new coils....But I had a killer TAF that had stuck coil sleeves but could crush every shot so don't let that freak you out.
2) as a start get a minimum rebuild kit that replaces EOS switches and plungers and not brackets and coils unless 1)
3) replace the flipper cabinet switches if you are not happy after that and play, play, play
4) if you don't like the power at this point and want to get new brackets, look at the WPC upgrade. This is the only thing that really worked for me when the flipper didn't have the umph I wanted. FYI, I have had a handful of FirePowers and replaced the entire flipper assemblies on the first and it did nothing that the above couldn't beat.
5) have fun and enjoy