A trio of real estate finance trade groups is calling upon Congress to leave the GSEs’ guarantee fees alone as lawmakers devise a way to pay for tax cuts for the remainder of 2012.The Mortgage Bankers Association, National Association of Realtors and National Association of Home Builders dispatched a joint letter to House and Senate leaders late this week noting their united opposition “to increasing g-fees for reasons other than minimizing the GSE’s risk exposure.” Late last month, the Federal Housing Finance Agency directed Fannie Mae and Freddie Mac to increase g-fees on new mortgage products by 10 basis points starting April 1.