Circuit modeling of high-frequency devices described by tabulated multiport parameters has generated immense interest during recent years. In most cases, equivalent circuit models (ECMs) are available to the designers, which correlate well with the measured parameters at lower frequencies, however, deviate at higher frequencies. Traditional efforts to improve ECMs are device specific, laborious, and ad-hoc in nature. In order to address these difficulties, this paper presents an efficient and automated algorithm to identify appropriate frequency-dependent elements for adding to the ECM at arbitrary locations so as to correct for high-frequency errors. The new method enables the designers to retain their existing physical models while providing a means to capture the high-frequency effects accurately.