I was hoping someone could help me with an EFIS issue. I have the GRT 2 axis autopilot in the plane. I am using an Garmin 250XL to drive the EFIS on channel 1. During start-up the EFIS confirms the GPS signal. I can set the autopilot at altitude and it will hold heading and altitude. However it only tracks the heading bug. When I try to have it track the GPS course it wonders off course immediately. I have tried adjusting the gain with no luck. The BAUD rate is set correctly from the GPS to the EFIS. Is there something I am missing? I have even wired in the iFly 720 GPS to the EFIS on GPS channel 2. It recognizes the GPS input (no faults) and it does the same thing, wonders off course within a second or so. If I let the airplane continue on the autopilot it will turn away from the course line to a random heading and just keep going with no solid direction. As stated heading bug works great but it will not track a GPS course line. Note: in the past these two GPS's drove the TRIO system perfectly.