The inlet chamber has inlet ports communicating with {HEAD ~ exhaust pipes} respectively and the outlet chamber has {TAIL ~ an outlet port} communicating with a downstream exhaust pipe 
The inlet chamber has inlet ports communicating with { HEAD ~ exhaust pipes } respectively and the outlet chamber has { TAIL ~ an outlet port } communicating with a downstream exhaust pipe
OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH