I would suggest replacing your plug wires next, also. My 98 was doing the same thing as you have described. A new set of Autolite plugs and wires from Advance Auto Parts (about $75) fixed it.

Steve

98 Contour SE Sport 2.5 Duratec ATX The wifey's car 89 Taurus SHO - 246K miles 94 SHO ATX - 190K 1997 F-150 5.4L ATX - The Workhorse 150K. ANY THREAD WITH "OMG" or "WTF" ETC IN THE TITLE WILL BE IGNORED!