I am always surprised when people argue with me. Why ? Because I almost never say anything which is not standard industry wide information.. thus my answer can be easily checked either by Googling or a quick look at places like Aircondition.com.....
The venturi pump abilities are inherent in the physics of how it is made... don't trust me on this... check it out...

I can not say if all R4's are the same... so I did not say anything concerning used VS new... much has been posted in the archives on this stuff though..if you want to do a search.....