I used my stock maf tube. However the top section of it was over 3" and I couldn't fit the coupler over it.
I took a dremel to the section of the maf tube that holds a honeycomb screen. I cut off a total of maybe two to three inches. If u look at the stock tube you will see there is plenty of tube to couple onto if u cut that top wide section off. However there's no reusing it on the stock air box obviously.
“Who you are speaks so loudly I can't hear what you're saying.” -Ralph Waldo Emerson.