Quoted from CNKay:Yes the 20095 are more powerful for sure.
I think that is the strongest stock gottlieb coil.
It is.
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While a stronger coil will definitely add some amount of power, when was the last time your flippers were rebuilt? Especially on Gottlieb's that are 30+ years old, the hole on the plunger link will wear/widen over time and, as you may already know, this causes the flipper action to become more loose. Loose = less power. Dirty sleeves can cause drag; worn top and bottom bushing give to loose action; sometimes the coil stop or even the plunger can become magnetized which will also potentially decrease power.
I understand having the machine at a higher pitch than the design intended means you're asking the flipper coils to do more than they were intended for, but I would recommend taking a look at a rebuild kit, only $33.10 from PBResource..