Guys, help me clarify this one. Gutted pre-cats only on an RS4 main cats intact. O2 spacers should not be necessary since the downstream o2 sensor still has a cat in front of it? I sold my piggies to another RS4 owner and there is a little confusion on weather or not he will need spacers.
I think no matter what it is S4 or RS4 you still need to move the rear 02s past the main cats if you dont want a CEL. that or get the JHM tune