Long term storage & overdrive hesitation
 

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I have a 1986 RX-7 GXL with A/T, bought new. Since I live in Maine (salt eats cars) I store it for the winter. The question is:What can I do to avoid the many mistakes (expensive) I've already made?
I use stable.
I start it up 2 or 3 times, bring iy up to temp, and roll on the tires a bit to pick a new flat spot.
And oh yea, run the A/C to keep the seals wet.
I run up and down the gears with my foot on the brake.
Since I drop the insurance, no on road exercise.

So far I've most of my freon one year. It has not happened since I started cranking the A/C during my winter startups.
I've had my injectors gummed up (really expensive).
This year, and to a lesser extent the last two years, it hesitates when shifting into overdrive, just at the shift point and a little beyond.
It loves the other gears a the high RPM's; but when I accelerate quickly in overdrive, not enough to force a downshift, it bucks and hesitates and makes difficult to increase speed.
I've had a complete tune-up.
The transmission flushed. (I've never heard of that).
And the engine decabonated. (whatever that means).
Since I had nearly a full tank of 87 octane, I added octane booster and ISO dry gas.
I've just about got burned out and plan to use only 91 octane.

Any suggestions regarding storage and the problems it may cause or my overdrive acceleration problem would be greatly appreciated.