I've experienced the same issue with flipper strength on Gold Strike. In my case it turned out to be slightly lower line voltage that wouldn't give the flippers enough power (they had been completely rebuild). I think there was also an issue with the game having an incorrect front/back leg size. My Target Alpha didn't have a weak flipper problem, and I'm guessing it had to do with the different style of flipper mech, even though the same coil was used. The older style mechs aren't as rigid.

There are also yellow and orange dot 5141 coils that PBR sells that will increase the power on the flippers a bit. I've found they helped on occasion, especially on the older style games.