Im using pehkui on a server and it is causing the error of wrong mod lists. Any help? also I've already checked to make sure it was this mod causing the error.

Closing due to inactivity. If the problem still occurs with Pehkui 3.1.0, please open a new issue.

you maybe missing a mod
or you need to re add all the mod on server and game

I've tried re-adding and copied all the mods on the server over, but it still doesn't work, so I'm not missing a mod.

Can you check if your issue still occurs when using Pehkui 2.2.0?
Also note that the Forge version of Immersive Portals doesn't have support for Pehkui yet and therefore doesn't have size-changing portals currently.