My planes do have a tendacy to climb when power is applied and I am aware of the problem and in the process of fixing that. I will try a range test with a friend and see if the elevator moves, but like I said before, I can be flying nice and level with a steady throttle and the planes will turn and go straight up. And it happens FAST! Faster than I can reproduce with the elevator controls!

I appreciate everyone ideas! Keep them coming so I can figure this out. I have a feeling that it is wing gusts, as it doesnt seem to happen on very calm days. I have also checked all the linkages and the are in good condition, without any freeplay.