evaluating {TAIL ~ a conversion capability} of the catalytic converter volume on the basis of a value which is a function of the first difference, the value being normalized to a value which is a function of {HEAD ~ the second difference} 
evaluating { TAIL ~ a conversion capability } of the catalytic converter volume on the basis of a value which is a function of the first difference , the value being normalized to a value which is a function of { HEAD ~ the second difference }
OTH 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 OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD