Turn your sensitivity up all the way to start. Then Noise Cancel, Auto GB, and after that back the Sens down until it becomes stable.
Coiltek coils are HOT, so don't be surprised if you end up with Sens set in the 20-24 neighborhood.
Also, it's a big coil that's looking at a lot of ground, so sweep speed needs to be slower to allow the machine to properly respond and ID all that it sees. Be sure that you're going slow enough before turning Sens down. And after that, any falsing that occurs can be an indication that you're speeding up.