So my x308 xj8 went to the mechanic because of the restricted performance light and CEL. So he cleaned the Mass Air Flow Sensor and the Throttle Body. But he checked the check engine light and it was misfire cylinder #7 but then the Brake light came on and he told me press the brakes i pressed it and it gone away but then all these warning messages came on my screen like BOOT OPEN, ASC Not AVAIL, Trac Not Avail, ABS, etc... So i drove home and the lights went away except CEL and Restricted Performance, I shut the car when i got home, couple mins later i started it drove it the light went away.

My mechanic also cleared the CEL light but it wouldn't authorize it but it went away...Is this a battery prob? pretty new battery

 

I would have the battery load tested, but if as you sat it is fairly new it's probably not the problem.
I would say that it is definitely a voltage problem from all of the warnings. I would start looking at the grounds. First on the list is the ground strap from the engine to the chassis just to the rear of the passenger side front wheel.
I would then check and clean the battery connections and the end of the negative cable where it is attached to the body.
Next I would check and clean the ground for the ECM module. Any loose or corroded ground is going to give resistance to voltage and affect the signals on the CAN Bus.
I realized after thinking about it you have been doing some major supercharger repairs. You might want to go over each of the connectors and make sure they are all seated. A loose connector can also create the problems you are seeing.

 

Thank you so much, I will do this today!