Fixed (I think)
 

I siliconed the vaccum lines to make sure there were no leaks (part of my temporary fix until I can order a new porsche-original cheap plastic vaccum harness to break again unexpectedly in the future) and WHAM! perfect running car. No bucking, no skipping. Purrs like a happy kitty. :)

Much thanks to everyone for their hints / tips though - I've got a better understanding of the fuel system now.

Hey, congrats....

Never thought about that one.

If it aint the grounds it's the vacuum!

True dat.