I was taught right post first with my TDI course although the instructor did mention there were other ways but he preferred that one but there was no right or wrong. Same with other aspects on the course related to kit config and so on - TDI seemed to have a work with what you've got rather than just tell you things must be done with this and that way etc.
The theory being if you know for certain where its coming from (reg in gob freeflowing, right post, reg under neck freeflowing, left post, anything else or unsure then isolate and work it) you can save more than half the gas.
Others obviously disagree.
I did it his way as it was the first way i was taught. I reserve the right to reconsider and possibly change my mind at any time though
