Hello Kurmit,
Check out my website
www.OrangevilleAirsoft.ca I can help you out! You will have to be a bit more specific on what type of M4 you have. I think what your are looking for is an ETU, Mosfet, Speed Trigger, Motor and Gearbox Shimming. This is what I generally tell customers who are looking for that snappy trigger response in semi.
I look forward to hearing from you.