Like Nicholas I replaced my wires and plugs and it now runs smoother than never. I don't know if they put cheap stuff on there but I know that the new stuff is good. If you decide to get the wires and plugs changed I strongly suggested you go with good products since they usually have better milleage ratings...
Hope this helps. It sure helped for me. BTW, I'm not an expert but I know when my engine runs hard or smooth
