After a few weeks of searching and replacing stuff I finally found the cause of the rough idle(and gasoline smell) --> The spark plugs

Before the replacement:
-Rough Idle (but ran good with higher rpm's)
-unable to set the idle due to unsteady rpm's (the idle was way to high, had to correct a great deal afterwards )
-Strong smell of unburnt gasoline

The plugs looked "ok" when I pulled them (two of them were a little bit burned at the edge, but could have been just a little rust too, so not too sure since it was really minor)

I've got no idea how the wrong (or just too cheap or whatever) spark plugs caused such a huge impact, but I enjoyed a long and relaxing ride the whole weekend

 

Glad you nailed it. Plugs are one of those things where if they look bad, they're bad. If they look good, they could still be bad (applies to a lot of stuff on the "high voltage" side of the ignition).

Having an extra set laying around to throw in, just in case, is always a good idea.

 

Thanks! Will do