[Spanky McGee]

I'm going to pitch my High-Flow cat soon, and run a 3" DP straight back, but I'm sure to get a constant CEL.

YMMV

 

[Spanky McGee]

Would welding the O2 sensors back into the pipe help at all?

Good question. But it isn't the LACK of the O2 sensors that causes the cel. The ECU wants to detect airflow through a CAT if you have one or not. Hell, Even my High-Flow cat causes codes every now and then:

"CAT Below efficiency"

Here is a picture of the set-up I'm installing. Notice the DP STILL has the O2 sensors. The computer (until the stand-alone comes out) will read this as a fault, and give a CEL.

Bummer.