Using Some plex in a 4 or 5 inch circle. With the head on top and the shop vac under neath. Then you can use strings and smoke to tell how things are flowing. Strings are really important for flow bench testing. And you dont need an expensive meeter and test unit that will not be acurate from day to day.
If you use the maf be sure to use a regulated power supply that can produce the same 12 v everytime. If it delievers more volts when it gets more volts it will screw the readings. Everytime you wife turns on the dryer you port work will be better. One of the main reasons home made flow benchs dont really work cause ypu need lots of tech equipment to support the meeter and reading of the meeter.
String always works if a little low tech. Also works great with smoke.