Failure code
 

this is too weird, we have a 1998 Ford Windstar with a 3.0 Liter engine. A while back the "Check engine soon" light came on, we purchased an OBD11 code reader, the onboard computer and code was a P0430 Catalyst efficiency below threshold bank (2). Okay, we installed two new O2 sensors on the catalytic converters. We cleared the Code failure, drove the car for weeks and the failure did not appear until we drove down the same highway and only this highway where the check engine light showed up. My only guess is, is that the converters are bad. Has anyone had this similar problem?