i am currently experiencing a similar issue with my '94 8v.
Had a full service, throttle body cleaned and new timing belt and tensioner.
The car (prior to service) seemed as if it was misfiring as cruising speed, around 2-3k revs. This felt like a millisecond where the engine was not giving any power. This wasnt noticable to my missus or other people, but i could defo tell.
Anyway, after the service the car ran really well, was quieter and felt alot more responsive.
This went on for a good few hundred miles. Now the car has started the slight spluttering again at cruise speed, also slightly noticable on acceleration. The idle speed varies very slightly too, not enough to move the rev counter from just under 1k which it always sits at on idle, but you can tell it fluctuates.
The power itself is always there and it is still just as fast if i boot it, its just the annoying splutter on the motorway and cruising thats is getting me.
My car is running a bosch/digifant set up. Any ideas on this and the post starters issue?