I have found an easy, fast and inexpensive fix to my check engine light (cel light) issue. What is more unbelievable is that it is easy, inexpensive, you can DIY and is reversable. Did not want to pursue an electrical fix by splicing into the cel harness and adding some kind of capacitor or resistor. After resetting check engine light, have driven over 100 miles and no cel light!

You need to purchase 4ea. Anti-fouler spark plugs. They are packaged 2 to a pack so, you'll need to purchase 2 packs. Cost @ $4/pack. I found these at the neighborhood NAPA auto parts store. Part # 730-2443. These actually a 18mm spark plug spacer designed to move a spark plug further out from the combustion chamber for older FORD's that burned oil. It is not some kind of special spark plug.

1. You'll have to do a little machine work to fit your 2nd. 02 into this Anti-fouler. With the help of my dad and his metal lathe. Take 1ea of the Anti-fouler (AF) plug and insert a 19/32 drill bit into the AF. From this point you will drill out .175 of the AF (.125 = 1/8" - .250 = 1/4"). BE VERY CAREFUL not to drill too deep as you will ruin the AF by coming out of the threaded part on the other side!
2. Once you have successfully bored out the AF. Take this same AF and drill all the way through with a 15/32 drill bit.
3. Now assemble before installing on exhaust pipe as you don't want to over torque and ruin the precision work you did in step 1.
Take the newly machined AF and screw into the back of the other AF that came in the package. Next take your 02, coat with anti-seize and screw into the back of the machined AF.
4. Coat other AF with anti-seize and insert into exhaust bung and torque down.

I believe that this solution moves the 2nd 02 sensor out of the direct hotter exhaust stream enough to fool the engine check light so it falls back into a closer to stock fuel trim range of .2-.8 Volt range. Someone can chime in at this point if my thought of why it works is slightly off. What I can confirm is since installing, have driven the car in city traffic, highway cruising and full throttle red line (Open and close loop engine situation) and no dreaded cel light!

I'll bet that this will also work if you decide to run a cat bypass pipe...

Good luck!