Tried to convert to a cone filter but the EX is not having it

[Black92LX]

I have done this on a couple vehicles with no adverse effects and gained a couple miles to the gallon which was my hope here.
I made an adapter to the MAF to put a high flow cone in place of the stock air box.

Started it up and idled fine for about 10 minutes and then it started to sputter and want to die. Above 10mph it was fine but under 10 mph would buck like crazy and kicked a CEL smelled like fuel and read a rich o2 sensor then finally died. I reset the ECU and tried again but had the same problem.

Any thoughts on why the ECU isn't able to adjust it's fuel map.
It's a 2003 4.0l Flexfuel Explorer.

 

[Limited02]

I would try to clean the MAF sensor because sometimes some filters come with a little extra oil(K&N to be more specific) and coat the MAF sensor. Check all connections and make sure you have no vaccum leaks as well.

Another thing, since you have no shield, I wonder if the motor is reading extremely high intake temps(after motor warms up) and pulling timing or something?