The MaXsys S4966V2 (part No 03-25328) is available for ULSA/Rheco units dated from 1st June 2017. Please see the TU-ULSA Burner Control Update for more information.
Is the MaXsys S4966V2 burner controller still available?
Looking to upgrade your old heater? Look here for information on which product is the best like-for-like replacement.