Heat performance tune up times three systems. Cleaned all flame sensors. Tested all safety features. Changed out 20 by 25 by 4 filter Tom supplied. Systems operating at MFG specs at time on all systems but the master. Master is oversized and has an outdated bypass and is going off on a high limit error code. This was shown and explained to the customer along with the solution of a lower fan speed which he declined. High static will result in poor performance, blower issues, and shorter life span. Many of the registers are wring and blow directly onto or into the area of the thermostat. Can confirm heat is running on all systems at this time