I have a 2012 B40 with RayMarine E90 chart plotter and ST70 autopilot. When my autopilot is on it shows that it is reading magnetic heading, however when i turn on the E90, the autopilot switches to True heading, which is not good because of the variation. I contacted Raymarine and they want to know which model autopilot course computer is installed. I have no idea where to look or where this computer can be. No reference to it in any of the materials provided to me when i got the boat. Anyone out there having a similar problem, or can tell me where to find the autopilot course computer?