I have very similar problem with mine ('91)........
Sometimes.. when stopped at traffic lights on the level the car will barely move when I lift my foot off the brake, sometimes it creeps normally before I touch the accelerator
Sometimes.. when braking I notice the response it more positive than other times.
Sometimes.. the gearchanges are really sweet, sometimes they are quite harsh.
Sometimes.. the acceleration is really positive, only having to literally touch the pedal, sometimes it is quite sluggish.
All the above relies on the vacuum system so I am lead to believe this is where my problem lies, but where to start. I read on another forum that the main servo pipe (proper name?) that leads from the intake manifold to the brakes servo can become brittle or very soft. Spiders have also been known to settle in these ! I will try to take mine off, blow throgh it and see if that makes any difference.
I understand there is a vacuum module on the side of the gearbox, I have not been underneath yet. Do these items fail or perish?
Where else should I look?