Hi I am looking for some opinions on what the best way to build a cold air intake is. What are some good filters? What should the flow rate of the filter be? Is it better to run 3" pipe all the way from the turbo back, to prevent turbulence from down sizing? Or run 4" and reduce it to 3", to increase volume at filter and the beginning of the piping? And does a box around the motor side of the filter do anything at all as far as getting colder air?