I've used the output air from a shop vac and a water manometer to do comparisons between ports at various valve lift settings. All it takes is an adapter between the vac hose and the port which can be positioned accurately and a flow control valve to bypass some of the airflow to prevent overloading the water column. The setup I built cost less that 50 bucks in supplies, and took about four hours to build.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!