{HEAD ~ The flow} into {TAIL ~ the exhaust purifying systems} may also be controlled according to engine speed 
{ HEAD ~ The flow } into { TAIL ~ the exhaust purifying systems } may also be controlled according to engine speed
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH