It's simply not possible for us to troubleshoot everything you may or may not have done to the ROM since installation. The lag could be caused by an application you've installed (either from the market or from a website), could be caused by improper settings in SetCPU including using s battery saving governor on your profiles (other than screen off), setting the CPU too low, could be caused by a kernel you've loaded (if you did), could be caused by, could be caused by (i think you see where I'm going)
Here's the best suggestion I can give. Do a complete wipe (Factory/dalvik/cache), flash the ROM, and don't change or install anything. Use the ROM for a couple days AS IS before you start loading anything or changing anything.
Keep in mind there's pages of people getting 20, 30, 40 hours with this ROM. Unfortunately an improper setting or poorly coded app is going to impact any ROM and it's outside of our control.