Okay to test the function of the strain gauge connect up to your OBD2 connector or wirelessly if you prefer, open the tuneboy software so you can see the main display then go to the view menu and select target screen, this will show a small window that has within it two boxes for A/F front and A/F rear cylinders , they are readings from your O2 sensors which you have discnnected ( at least one ) to plug your strain gauge into, two if you have fitted the nudge buttons , with the ignition on there should be numbers in green of around 13 -14 to 1 if you now apply pressure to the strain gauge the display for the cylinder you have it plugged into should change to from memory about 7 to 1 then if you apply pressure the other direction it should change again. That will confirm the strain gauge is either okay or faulty.
Good luck let me know how you go