I have exactly the same issue. I have been trying to increase KFKHFM by percentage as bigger the intake husing is. So my actual housing internal diameter is 3 inches and my understanding is that stock diameter is 2.5 inches. So, calculating area the of 3 inches versus 2.5 inches diameter, the area is almost 50% of difference, in that case I will increase and multiply the stock KFKHFM by 1.5.
Or what do you think?
U need to rescale MLHFM. I would recommend by 1.6.