I also have the "fast flasher problem".  It started when I jury-rigged a fix
for a corroded turn signal lamp socket.
The turn signal flash rate is about twice that of the emergency flash rate.
I don't understand how the flash rate is determined.  It's the same relay
and the same lamps for both functions. By operating either the turn signal
switch or the emergency flasher switch 12V is placed on the turn signal
bulbs through the flasher relay.  Apparently the flasher relay can sense the
current flow and operates to turn off the turn signal bulbs and turn on the
turn signal indicator lamp on the instrument panel.  The flasher relay then
turns itself off thereby restarting the on/off cycle.  Maybe the amount of
current
through the flasher relay determines the timing and since my electrical
contacts at the bulb sockets are poor it could affect the timing.

John Bates
84 GL

Fairfield County, OH, USA