Forget about thrust and incidence angle. Any airplane in level flight has a specific speed and angle of attack. An increase in speed requires a lower angle of attack and a slower speed requires an increase in the angle of attack to maintain a constant level of flight. An increase in throttle at the same angel of attack for level flight will result in more lift and the climb you are experencing. To maintain level flight as you increase speed you must apply forward stick pressure(down elevator) and conversely you must apply back stick pressure(up elevator). If you have a programmable radio, you can program a throttle increase with a corresponding down elevator and thus level flight. This will require some experimentation as to how much elevator is needed. This is a rather simple explanation of a rather complex subject, but if you want a detailed explanation read Chapter 1 of Wolfgang Langewiesche's book Stick and Rudder.