When {HEAD ~ the device} is subjected to {TAIL ~ the intake manifold vacuum}, the upper half of the elastic coating reacts by varying in size to reflect the magnitude of the vacuum 
is subjected to
When { HEAD ~ the device } is subjected to { TAIL ~ the intake manifold vacuum } , the upper half of the elastic coating reacts by varying in size to reflect the magnitude of the vacuum
OTH HEAD HEAD HEAD HEAD HEAD HEAD REL REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH