Have you tried a smoke test yet?
Ed
I’ll make a smoke tester tomorrow to try a smoke test 
Finally had the time to do a smoke test today…
I found a leak at the connection of the pcv with the lines coming from the valve covers.
I’ll fix this tomorrow since today is a national holiday and the shops are closed. But I highly doubt that this leak can be the source of my problems 
So I fixed this leak but the car still misfires. Now this seems strange to me but the car seems to start misfiring when put in D or under some load of the transmission.
When I leave it in P or N it goes perfectly well…
Van someone shine a light in this
The only thing of note is that you are putting pressure on the power train when you engage the transmission.
So you are still getting all the same codes as your original posts?
Ed
Yes codes are still the same.
Intermittent random misfires and misfires from cilinders 1 to 8.
Only under low load…
So to stop the misfires you have to feed more throttle/revs or let the engine run free (park or neutral)
OK i’'m out of ideas…
I made an appointment in a month with a specialized shop, they’ll do a transmission flush and troubleshoot the car.
This goes above my understanding…