How to increase mic gain with 6.0 mm mixerpath.?

I use my phone a lot for work but when im on the phone i hear "what did you say?" all the time. So is there anyway someone can help me increase the mic gain.? Ive tried well over 5 roms and it's still have low mic gain. The only rom i dont have problems with are the official rom(stock) and thats it

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