I have a 20Z 953 that left the factory in '84 with an open ROPS and a heater and a cab air intake and filter. In '95 an aftermarket cab from Kenco was added which made the cab air filtered intake nice, but not necessary. My question is why Cat would put the intake system on an open ROPS machine. Local parts people say the intake system was used in conjunction with cab a/c which this machine NEVER had. I know Cat put heaters on open machines but why the intake system? Any insight???