Big thanks to @
GrimmSpeed !
Finally, I've got a working cold air intake system for my car.
I've tried various intake (aFe, Injen, K&N) and they got the same exact problem.
In WOT situation in low RPM (below 2000RPM) the engine was running like crap. Pass that zone, all the intake that I've tried give decent gain.
But the GrimmSpeed one deliver good performance and don't have that low RPM problem like they all do !
Could be added as a note somewhere, I did forget by mistake to install the seal between the snorkel and the Grimmspeed air box. Just because of that, the air flow was deviated somewhat and caused the same problem I had with other intake. I've installed the seal and well, everything is working fine now !
The only "problem" of this intake, it's a bit too close from the oil sensor connector and it do rub on it.
EDIT: I've reajust the air box and it fit correcly now !
Thanks a lot !