gas consumption increases after spark plugs & wires are changed.

2000 lesabre limited.
I found the gas consumption increases after I had spark plugs & wires changed. Now it is about 14L/100KM, while about 11L/100KM before the replacement.

I also found that the length of the new wire set and old wire set are different. The plugs are the same.
New wire set model: ACDELCO Part # 9746DD {#88862390}
I don't know the old wire set model.

Spark plugs are ACDELCO Part # 41101 http://www.rockauto.com/catalog/images/MoreInfo.gif {IRIDIUM #12565030, 12568387, 25330840, 41978, 41984}
SPARK PLUG .060 GAP

Anybody know the sequence and length of the wire set for 2000 lesabre? I appreciate your help.

I would question the wires you had installed. Part # 9746DD is a low-end universal wire set, which probably has a higher resistance than the OEM replacement Part # 746DD; however, that alone should not cause any substantial decrease in mileage unless you have misfire. I would also look for any loose or broken vacuum lines and check all plug wire terminals for good contact on the plugs & coils. Sometimes it is difficult to here them "snap" when installing new wires. Of course, if you have a misfire, that should show up on a scan and tell you which cylinder(s) is the culprit!