Ok, from now on I won't underestimate a fuel filter ever again .
Looks like your first guess was right djmillsy . Changed out the fuel filter yesterday (the one that tought it up to put it under the car should be shot) took a testdrive and the problems seemed to be gone apart from 2 little hicups at low revs.
Took another drive today, chucked in another bottle of injectioncleaner to get rid of any residue from the dodgy filter and it still runs perfect.

So a big thank you for your efforts and suggestions guys