Modulation may be low with some noise canceling microphones.
ACTION: If modulation is low with an aftermarket microphone, then change R178 and R182 to 82Kohm.
See images for the location of R178 and R182.
NOTES: It may be easier to access the resistors if you temporarily remove C147.
If at some later date a different microphone is used (one with a higher audio output), it may be necessary to turn down the Mic Gain.