I350-T2 WAN Throughput issue on bare metal

LordL

Hello,

I'm somewhat new to PFSense, and I have a throughput issue I don't understand. Basically I am only reaching ~800 megabit/s through my PFsense box when I use an i350-T2. When I connect directly to my ISP's router I can reach ~950 megabit/s. I have already tried the "Hardware Tuning and Troubleshooting", but none of the settings affect my throughput.

So far, it looks like the issue only happens if I use an intel i350 as WAN on bare metal, see my tests below.
Pfsense hardware: bare metal. i3-10100, h470 motherboard, 8 GB ram, SSD. i350-T2 PCIE. Onboard i219V (compiled by me). 1000 megabit from ISP.

My tested setup:
setup 1:
PC <--> ISP router
Throughput: ~950 megabit/s

setup 2:
PC <--> (LAN:i350#1) PFSense (WAN:i350#2) <--> ISP router
Throughput: ~800 megabit/s

setup 3:
Interestingly enough, if i try this setup
PC <--> (LAN:i350) PFSense (WAN:i219V) <--> ISP router
Throughput: ~950 megabit/s

setup 4:
However, if i try the reverse:
PC <--> (LAN:i219V) PFSense (WAN:i350) <--> ISP router
Throughput: ~800 megabit/s

side note:
I tried the i350-T2 PCIE in a hyper-V PFsense using two virtual switches on an another machine (similar to setup #1), and as I remember I was able to get ~950 megabit/s.

I don't understand why only setup #3 gives me the desired throughput, and I have no idea how to continue my troubleshooting with setup #1.

Any advise is greatly appreciated.

LordL

*I meant, I have no idea how to continue my troubleshooting with setup #2