CPU idle around 3.7 GHz (XPS 15 9570)

Hi, I followed bavariancake's guide to getting macOS Mojave running on my XPS 15 9570. I've got most of the stuff working, but one big issue is the battery drain. Using Intel Power Gadget, I see that my normal CPU frequency is around 3.7 GHz despite the base frequency of the CPU being 2.2 GHz.

This causes fast battery drain, and I've also noticed that the computer keeps generating heat during sleep (it stays warm in my backpack) and battery keeps draining about 10% per hour.

Is this normal? I've tried many things to get the CPU frequency down (including undervolt with VoltageShift) but the issue persists. Any help would be appreciated.

Thanks!