Performed preventative maintenance for a high efficiency Lennox furnace. I observed the system starting normally. I took a combustion analysis test and got the following readings, o2 is 13%, co is at 7ppm and the system is operating at 93%. The amp draws for the blower motor is within normal range. I observed the system starting normally once it reached the desired temperature. I removed and cleaned carbon off of the flame sensor. Cleaned out the burners and burner box. Checked all electrical components needed for heating. Homeowner recently replaced the air filter Merv-11 20x25x4. The system is getting error code 225 which is an error code for the pressure switches. Due to the system being under warranty it is recommended that the collector box, inducer motor and pressure switches should all be replaced to prevent any issues in the future. See estimate for details.