Gotta take the BC645 mic apart again. I did a little reading on it. Found out it's has condenser mic element in it. Also I read an article on some taking the guts out of a Uniden pc 68 hand mic and transplanted it into a chrome road king shell with a little plastic glueing to adapt the PTT switch and used tin foil for shielding.
I won't do that but do the same mod I did on my CRE-8900's stock mic in enlarging the hole in front of the mic element. Hopefully the mic element is still good. It stopped working soon after I resoldered the lead on the back of the element or just buy a new one for under $15 at Amazon.
I think one thing I did wrong in reassembling the mic element is that I pushed the element too close to the mic grill and not back towards the rear. The rubber doughnut that the mic element is housed in acts like a noise canceling mic in limiting any sound that is not directly in front of the mic.
How I built my Best CB Mic Ever!
Amazon.com: Uniden BC645 4-Pin Microphone for CB Radios: Car Electronics
P.S. I think that the BC645 mic with it's condenser mic element beats out most stock mic's. The only one that I think so far that comes close is the Galaxy/Ranger stock hand mic sensitivity wise