what is the vacuum cylinder that looks like a ball cock by the passenger side head lights/battery box on my 89 classic for????????:confused:made engine mounts for 200tdi conversion used originals and abit of fabrication

help i'm changing my 87 classic from petrol to 200tdi engine and box came out of one that i had but broke up.all married up ok.ooooooopps engine mounts no fit boo hoo. doner long gone.is there an adaptor plate or do i have to cut my mountins so i can fit donut type mounts.

my 2.5 p38 seems to be changeing gear at to high revs any bright ideas