6 and L5 are AM power / D-14 is mod limiter . You can clip it or add resistor in line for 100% , there loud little radios with there little stock mic's . Talkback , should be able to take 100 ohm or lower resistor ,solder from receive pin (4) on the mic jack to board ground , this should give you talkback , the lower the resistor ,the louder it will be.
...........Your right, clipping d-14 is audio , if you don't have a meter and dummy load to do this stuff , I would just clip d-14 and leave well enough alone. D-14 will make the radio louder and the pep swing will be automatic after that. If you have a meter and you can tell what the power is ? Take it up and back it off a bit from there. Theres' no need to bore it out. Those are good RX/TX little radios . if your not sure ? just clip D-14 and be done with it.