Does NAT reflection impact on performance?

[Phatsta]

I was just wondering what impact is would have since I'm seeing some strange numbers on my wan speed. It goes radically up and down and speed is far too low (maybe 25%) of what it should be.

I use NAT reflection for port forwards (Pure NAT), for 1:1 NAT and automatic outbound.

Just wondering. Because if I reset the pfsense and test speed, it'll be just fine. There is something in my config that's in error and I was just starting to suspect this.