98 Deville hesitates at 40-50MPH

My 98 Deville has just started running jumping like I'm running into a strong head wind at 40 to 50 MPH. The service engine light does not come on. I don't notice it at higher speeds. My 95 Olds 88 did the same thing a couple years back and the mechanic replaced the EGR valve and that took care of it. But at $180 for an EGR valve, I don't really want to "experiment" until it gets worse or better. Anyone have any ideas on this one? THanks!