<VV> Help Help

[McNair, Tim]

I have just purchased a 1966 Monza Coupe 4 spd 140 hp,, and after 12
weeks of waiting had the motor rebuilt and added petronix ignition stock
coil to it other than that it's stock,,, 

OK when the Corvair is cold or only run on a short trip 20mins or less
it has wonderful power excellerates well secondaries kick in and zips
through the gears like no-ones business,,, I love it,,,

BUT    once it's driven  for a short while ,, if on the interstate
steady speed it will start to "miss" or bogg if you try to excellerate
or climb a slight hill,,,,,, or if your at a stop light you must take of
slowly without kicking in the secondaries,,, it boggs sputters and some
times back fires,,,  
Bad advance ?? bad timming ?? bad coil ?? low fuel pressure ?? I'm at a
loss,,,, I suspect the coil may be getting heat soaked since it's
mounted next to the head,, but I have never owned a Corvair before so
I'm in the Corvair dark on this one Help Help Please,,
I'm afraid to take my car more than a few miles from home,,, but I love
to drive it,, 

Thanks
Tim