***FIXED UPDATE***
I have to say that I finally found and fixed the issue. The mains where too small making the engine running lean.
What I used :
primary main jet = 125, aircorrector = 180, emulsion tube = F50, idle jet = 55
secondary main = 130, aircorrector = 195, emulsion tube = F6, idle jet = 50
What should be used in a stock 4K engine with a Weber DGV 32/36
primary main jet = 140, aircorrector = 180, emulsion tube = F50, idle jet = 55
secondary main = 135, aircorrector = 195, emulsion tube = F6(under no circumstances do not use F66), idle jet = 50
Works like a charm.
Many thanks to altezzaclub and davew7
These two sources also helped a lot:
https://ratsun.net/topic/2125-weber-carb-hesitation/
http://www.3fowlers.com/Weber Trouble Shooting Guide.pdf