To be blunt, the System Idle Process *says* it is taking 99% of the CPU, but the usage in the performance tab reads 1% usage of core 0 and 20% usage of core 1 at idle.

Is it normal for Task Manager to contridict itself?

I wondered about that aswell when I was looking at a 95% cpu usage on system idle. I was like... wtf then a friend told me basicly to think backwards on that one.

System Idle is a lier, or its on drugs with its usless other windows fuction buddies

The percentage on the process list is how much of the total used process is in each program. If your CPU is at 20% usage, and you have one program using 25%, it's actually using 5% of your total processor usage.