Trackpad on MacBook Pro 8,2 (15'' early 2011) goes crazy on power
After much research, trial and error and thanks to others in this amazing community I've found out the reason behind my trackpad and keyboard failures. 

The reason is that my MacBook Pro was missing a Cable Bracket inside. Why was that bracket missing is because my MBP was candidate for the motherboard replacement program that Apple did for Early 2011 MacBook Pro related to the Video Card issue (more on this thread so I took it in Mexico City to an "authorised" distributor called iShop and I remember that was the last time I saw the part (as I reckon I changed the keyboard myself after a coffee indigestion).

So I hope my answer help any soul with the same problem!