[Jfrahm]

Yeah based on the surging it could be a classic case of a lack of fuel flow. If the filter has never been replaced that's a sensible thing to do as well as the testing of the DME temp sensor, preferably at the DME in case there are wiring concerns. If it's still boggy you could try to install a fuel pressure gauge you can watch while driving to see if the pressure is constant or see if it will pass a fuel flow test. The fuel pumps are pretty robust but they can wear out. It's also possible (but not likely) that the in-tank prefilter is badly plugged, I think it's the 928 part 92820108104.