Few facts about FeelThere ERJ:
1. It uses 2 engines
2. It not makes own throttles mapping
3. It not uses FSUIPC. During development FS9 Panels SDK was out and it allows make own TCAS without FSUIPC. APU that burns fuel and some other stuff I did with direct access to internal FS structures.
4. It uses KEY_THROTTLEx_SET events. 0-16k for forward thrust and negative values for reverse thrust
5. It's detects changes in throttle position (from keyboard, mouse, joystick or any other possible control), calculates from it new throttle position (not FS throttle, but throttle visible to user), then our internal throttle position goes to procedure that calculates new REQUEST N1 and at final stage requested N1, altitude, temperature it calculates position of FS throttle and sets it to that position.
Everething works fine until user not use some specific FSUIPC options. Have no idea where conflict is.