Upon arrival I began the furnace tune ups. This house has a total of 4 systems. I worked on 2 of the furnaces todays using their current membership to cover the cost. I checked the static pressure on both systems. They are both rated for a maximum static pressure of .5. Both systems were testing at the same reading of .68. I turned both of the blower speed taps in heating mode down 1 tap and that brought the static pressure down to .62. I checked the running amps on the inducer and blower motor on both systems and everything was within manufacturer specifications. These systems have a temperature rise rating that should be between 40 & 70 degrees. The main floor unit was testing at 50 degrees and the 2nd floor unit was reading at 45 degrees. I didn’t find any cracks in the Heat Exchangers at this time. I also did a CO test and found Zero PPM(parts per million). Both units had a Zero reading. I thought i smelled some natural gas so I tested each joint on the gas lines but found no leaks