Custom/diy cold air intake

I know there’s no benefits to a cai but I don’t have room for the stock one or an after market one. Anyone ever make there own cai with their own tube and filter?

I’m deleting the evap etc and not worried about a check engine light so will not having a port for the maf affect anything? What about the tube right before the intake that goes to the firewall, what does that go to?

picture for attention and of my space constraints



And a picture of the tube by the intake. It’s to the left with tape over it. Goes behind the motor and connects to something on the back of the motor but I can’t see

 

I still have the stock stuff and have the chance to trade for k&n cai. And is gone, evap canister is gone. Pretty minimal now. Just not sure what is necessary