Ok, that sounds like a thrust line issue. If it's pitching up when you apply throttle, and pitching down when you back off the power then you need a bit of downthrust or you need to shim the wing a little.

When you say it keeps climbing, do you mean that if you don't touch the thottle, and just point the nose up a little that the plane continues to pull nose up higher until it basically loops over on it's own? If that's the case, then a little reflex might help. You should be able to fly straight and level at full power, then pull sharply to a 45 degree climb, and the plane should just continue ona straight 45degree climb. If it pulls to vertical or beyond, reflex might help. Same thing downward, if you fly level at full power then push down, does the plane hold a steady down angle, or does it steapen the dive on it's own. If it keeps tucking in to a steaper dive, try a little reflex.

Since reflex is easy to adjust and put in and take out for most planes, I'd say give it a try and see if it helps. If you just raise the ailerons a couple of turns (don't over do it), and it doesn't help, you can just put it right back.