The reason it has been blocked off it because you have a Bailey breather fitted, thats all. The standard breather plumbs into the inlet on the left through another nipple, but when removed it causes a vacumn leak... no good on mfi obvuiosly. So. it gets blocked off. everything else can feed off the other side anyway there is no difference. As standard theres only 1 vacumn pipe, to the ECU, boost gauges and dumpvalves are aftermarket and people plumb them in with t-pieces.

"simples"