liamkirkham,

I just went through this myself and it took a couple months to find the problem. One of the most important areas to look at is the ground wire from the rubber boot unless your using a Bosch cap. Make sure it is grounded well to the block, a good place for the ground wire is to wrap it around the spark plug where you would put your wrench to tighten it and secure it with a hose clamp. If this is your first gasser you may think you have no metal to metal contact but you might want to take a second look or have someone else take a look at it. A second pair of eyes can sometimes see things in a different way. I know, that was one of my problems. Another thing you can do is to have the engine running and let someone walk away with the TX and once it starts going crazy disconnect one servo from your receiver. If your control sufaces are still glitching then plug it back in and try another. If you diconnect a servo and the gitching stops then you have found a bad servo. The thing to do is try everything you can that doesn't cost you any money first and hopefully you'll find it. My plane did the same thing as yours, range checked fine with the engine off but as soon as I started it up and got about 50' away it went crazy. That tells you that it's ether RF or vibration. My EI was bad.