What kind of vehicle are you working on?Have you contacted Irish Dave with your problem because he is usually very good about dealing with possible defects in the items he sells.I have one of his setups in my 56 and my buddy in his 55.Several others on the site have bought from him.If you are not getting any power assist and the freeplay in the rod is correct you possibly do have a defective booster.His products are good quality.I have heard of him sending a replacement even before the "defect" is in the mail back to him.Try contacting him.

  

And the model of car is ?

  AussieBill            YYYY    Forever Y Block     YYYY

 Down Under, Australia

Have poured a lot of time and money into a replacement dual res power brake and booster bought from ID in NM.System is sound,vac right up there.Brakes will not work.Going back to original Bendix Treadle Vac system but inspection shows inside of booster corroded and should be replaced.It is 6"diameter.Was wondering if later 5 1/4" unit would be a bolt-in replacement ?Would like to hear from anyone who has done this switch and any good source of parts(larger unit scarce around here).Thanks