The speed of the minecart is capped at 8m/s but the speed display included in the mod reads 40 m/s.

This video shows the issue, the minecart is moving at 8m/s as shown in the top left, but the display reads 40m/s as it is running on gravel.

Let me know if you need any more information or a mod list, I really appreciate the work you and other mod developers do to make our favorite game just that much more fun.

Mmm, yeah tough to say. Sounds like you have other mods installed. It's very possible one of them is interfering.

First step is to create a new world with only highspeed installed. Make a creative world and a simple test track. If you do that and you still aren't getting a speedup, then I'm not sure what's going on.

But my guess is it will work, and then you have a baseline for figuring out where the conflict is in your setup.

So It is indeed working in single player but there is something going on server side that is stopping it from working. I will continue to troubleshoot and report any findings back to this thread, thank you for your time and assistance.