XICMP much slower than mKCP?

[iopq]

I setup an mKCP server and got decent perf, about 40Mbps each way

when I turned on XICMP and fixed the id issue (it changes out of my NAT so I had to set it to 0 on the server) my speed dropped to 0.1 Mbps

When I did the FakeICMP trick with udp2raw I didn't see much performance degradation, but I used it to turn xhttp3 to ICMP so it's not exactly the same