In a case where the rate of interest on the debtors' residential mortgage loan was increased upon default, the District Court's judgment is affirmed in part and reversed in part where a "cure" under section 1322(b) of the Bankruptcy Code does not allow their bankruptcy plan to bring post-petition payments back down to the initial rate of interest, as a change to the interest rate on a residential mortgage loan is a "modification" barred by the terms of section 1322(b)(2).