17 hours ago, Phantoms said:

Make sure you've disabled the default trafficAircraft.bgl file by either editing the layout.json or overwriting the trafficAircraft.bgl file with the alternative method.

Ok, that indeed was the culprit. With the edited .json file, no FPS loss anymore on EBBR. Great. BUT what I now observed (I do honestly not know if this was like this before): on the VFR Map, I see the whole airport filled with planes (white plane symbols) at every gate, while visually it is empty. Does the VFR Map show the GSX ground vehicles as "planes"? Anybody else seeing this? Or is it an EBBR specific issue? Will check on other airports...

I give up. I've added several 1 hour repeat flight plans using AIFP and I see a couple planes flying between the two airports I used, but nothing lands, they just fly right by. And I see nothing taxiing. That is all I really wanted. Some GA action on the taxi ways. But nada. A couple planes parked but they never move. Waste of time focusing on this for me. Hopefully Asobo will care about it soon and fix it. For now I'll live with pretty nonexistent GA activity on the ground and refocus on the airliners which is what I have plenty of with AIG and FSLTL. I wish others better luck than I had in playing with GA.