Please Help, 1991 Passat 2.0 16 valves engine problems!!!

I have this following problem, I feel that it happens only when the
engine reaches normal temperature, I would be driving it down the road
and the engine would start to sputter, loose power, will not fire on
all cylinders and eventually it would just die, usually I would be
able to get it to go again and it would work fine and then after a
while same thing to the point where it would not want to start anymore
unless it cools down a bit. Now, I am suspecting one of those three,
ignition module, distributor or perhaps ECM engine control module. I
have tried to install different ignition module and the same problem
would persist. What would be the next alternative? I should also say
that I would have to be on the freeway going about 45-55 miles per
hour for this problem to occur, driving around residential areas would
not cause this to happen. Also, this is an automatic car, what would
you recommend for a smoother gear changing, the tranny seem to be a
bit hesitant when going into fourth gear, I would have to ease of my
foot for it to go in....not all the time but quite often..... If any
of you can HELP I would be really grateful...

Thank You in Advance
Marcin
[EMAIL PROTECTED](dot)ca