Acceleration issue

I have a 1996 Merc Sable, V6 3.0 12 valve, 125000 miles. Recently the engine light came on. Had the comp scanned to reveal a EGR code. I replaced the DPFE sensor and the light went out and no other codes came up. When I start the car cold then drive, it accels fine, but after it warms up, it appears to lurch, particularly at about 45 mph. Also as I slow down, it seems to downshift slowly so that when I accel again it feels like its slamming into low gear. Both of these issues dont happen regularly. At higher speeds it drives like a dream. Could another sensor be going out? Any ideas? Am I missing something obvious?
THANKS IN ADVANCE!