No power under accelartion

[Oldman]

This problem may be above my pay grade I reckon.

Worth reading through the Help & Assistance Section :
https://kombiclubaustralia.com/forumdisplay.php?fid=27

Particularly the  Bay Tech Clinic:
https://kombiclubaustralia.com/forumdisplay.php?fid=8
....and "How to & Handy Hints", 

Lots if proven info. in the Important Threads. at the top of each Section.

Above your pay grade ...?
You have a couple of choices 
Diagnose and learn from other's experience,( and there's lots here),  or find a reputable air-cooled mechanic and open your wallet.....wide.
It's the reality of owning a kombi unfortunately....approach it as a learning challenge.

In my opinion, getting  everything set to a reliable base line and maintaining everything in the best possible condition, the way it was originally set up, will provide you with the most reliable vehicle. If you are running the correct dizzy for the engine, the vac. advance line needs to be re-connected to the inlet manifold. The dizzy relies on the vac. advance can to operate the dizzy properly. A vac. advance dizzy without the vac. connected will always give you issues.

As has been said before, more often than not it'll be something relatively simple.....or a combination of simple things piggybacking to cause issue/s.
Good luck and please post up how you go.....it's how we all learn.