2004 Ford Taurus

Electrical problem
2004 Ford Taurus 6 cyl Front Wheel Drive Automatic 112000 miles

I recently changed the spark plugs at 100k bought them from napa autp parts and the wires. After I changed them I misplaced one wire, then I fixed it but after that, the check engine light came on. I rest the computer then after driving came back on, I took it to the dealer they pluged it said catalytic converter, then I replaced it. After 4 or 5k the light came back on and it says catalytic converter. I replaced 3 oxygen sensors nothing happened. What could it be? I thought maybe mass air flow sensor or the 3 converter? Help!
November 12, 2008.

Lets start with what do you have for codes 1st?
also check for vacuum leaks

need manual CHECK IT @

Nov 12, 2008.