Power on the pull out shouldn't really be a problem. You are pulling back on the cyclic all the time. This offloads the engine to a certain degree due to the flare effect.

It sounds that maybe your loops are a little small (i.e tending towards flips). These will require a load of power. For a normal loop you need to make sure that you are running in at full speed (i.e straight and level with the collective all the way at the top) before you pull up and pull up smoothly.I think the most likely point to run out of speed is at the top of the loop. The pull out can be flown with very little collective.

Don't take what I say as gospel. I am only at an early stage myself. I taught myself to loop and the above notes are based on my experience.