the defi, EBC, and haltech sensor can all be run off one line. But id leave the
BOV on its own line as that line generally has to be a bit larger to make the
BOV react faster.
I remember you can buy this little thing that centralises all the vacuum lines into one neat little unit and helps to keep all the sensors reading the same value. Its called a "vacuum manifold" IIRC. Using many or mutliple T pieces on one vacuum line can result in minor differences in sensor values during pressure changes.