The fugitive gases and {HEAD ~ the air} enter {TAIL ~ the engine} 101 from the air intake 120 through a control valve 133 
enter
The fugitive gases and { HEAD ~ the air } enter { TAIL ~ the engine } 101 from the air intake 120 through a control valve 133
OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH