The GM controllers have always been a weak link in the chain. Do as said above. If you want to you could run the Magic Pie without the small thin hall wires and get a 'sensorless' controller which will make the bike even more reliable and sturdy, the only down fall is you loose some of the torque. But saying that a good quality controller will let you pull more amps anyway.
Here's a good tutorial on easy wire lengthening.
http://youtu.be/7t9nT3Hn9b0 I use a 12fet Lyens 'sensorless' controller for my Magic Pie without the hall wires.
http://www.lyen.comEdward Lyen beefs up and will program the controller to your need. You can email him and tell him your spec and battery and he will help you out.
You could just get a 6fet 'mini monster' from him programmed for 25a and what voltage battery you use. It will take over 1000w peak. I see peaks of 1200 with this controller on one of my bikes. It is a very efficient controller made for long commutes.
Andrew