I have a 85.5 NA manual 944.  Somewhere along the life span of my
little toy, someone replaced the electrical system with one from an 88
or 89 vehicle (based on the fuse box) along with adding MSD ignition.
They MAY have also replaced the chip, I suppose I could verify that by
trying to take it past redline, but I don't really want to explore that
until AFTER I have had a chance to pull the timing belt cover to
inspect the timing belt.  I am pushing my luck street light racing as
it is.

Here is my question: I use 91 octane fuel (best I can find at local
stations), and I have noticed that after filling the tank, the beast
has hesitant acceleration for the first 25-35 miles.  This hesitation
reduces as the engine warms up but doesn't go away completely until
those miles have passed.  Once passed, the beast performs flawlessly
from 800 RPM to Redline, in at least the first 4 gears, and I haven't
had the guts to try topping in out in 5th so I don't know if it is wind
or rev limited (maybe someone can field that second question).

Anyway, it really bugs me that I can't top off the tank without
suffering from perculiar performance issues.  This is my mid-life
crisis car (WAY cheaper than an affair would be, by any standard) and I
need all the acceleration available to keep the testosterone flowing.

Oh, best way to describe that hesitation: ever driven with bad
wires/plugs? Feels like that.  No miss and I don't hear any pinging.
Rotor/cap/plugs are new.  Wires seem decent but could have 130k on them
for all I know.  But if it were wires, the problem wouldn't go away
after about a gallon was burned.