How And Why Move Emulsion Jets?

Pretty sure the new Holly HP’s with billet blocks are. My ProForms emulsion stacks were tapped to be adjustable.

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And again there is a "seemingly" modern metering block design and the IFRs are still at the top. I just have many questions. Like, if you move the IFRs to the bottom, do you need to plug the top holes? And WHY do they use "only" one pair of emulsion jets? And would "more" emulsion jets be beneficial? And WHY? And how do you tune for those? What symptoms do you look for to tell you which way to tune the emulsion jets......and on and on. LOL