1999 Mitsubishi Eclipse Surging and Sputtering

I bought my Eclipse at a salvage yard a year ago and recently finished completely rebuilding her. Recently, however, at VERY low speeds(in parking lots, etc.) Her acceleration has been surging. It felt like I was pumping the accelerator even though my foot was steady. She also has a rough idle at stop lights, which seems like maybe her EGR valve or a vacuum leak. Today, however, at the drive-thru, she started sputtering and misfiring, her RPM's dropped down to 4 or 500. We left, and at the next stop light she did the same thing, but died completely. I tried to start her back up twice, successful the second time and drove her home. Any ideas?