2015 ec300e

[Desert Silver]

I'm new to Gas Gas having worked on Jap bikes, CanAm's ATK's and KTM's. I'm in the process of rebuilding my son's 2015 Gas Gas ec300e that he bought from G Aaron. It was a Mag test mule and I have no idea how much time is on the motor. His complaint is while it has great bottom and mid it has NO top end. I'm in the process of tearing it down a little at a time due to the garage temps (triple dig and can only work for a half hour to an hour at most). My question is, what brand of piston was used in the 15 300 and is it a forged piston. How much does the billet head from RK tech help performance? I know I'll be coming back with more questions on this engine. Thank you in advance for any advice given.