Drilling spark plug non-fouler for test pipe CEL

[TBarCYa]

I installed a non-fouler to try to resolve the CEL with the test pipe on my 2.0T but still get the light. The one thing I didn't do was drill the non-fouler because I hadn't needed to do that on other cars in the past. The question is, what's the purpose of drilling the non-fouler? Is it to make the sensor fit the non-fouler or to allow enough exhaust to reach the sensor? I also have a little bit of exhaust noise from the engine bay at start up so I'm thinking the drilling is to get the sensor to thread all the way into the non-fouler which may resolve both of my issues.

[EvolutionArmory]

Give us a link to what you bought.

I just run a 90 degree spacer on my test pipe. No drilling or whatever you’re trying to do with what you bought.

[Jay-Bee]

I've sold plenty of non-foulers as o2 spacers, never heard of drilling one out, they should fit right in, something is off.

O2 sensors and spark plugs are both M18x1.5 thread

[vce1232000]

try one of these https://www.europaparts.com/oxygen-s...-mini-cat.html to resolve your cel

[TBarCYa]

The non-fouler fits the pipe perfectly and the sensor appears to fit the non-fouler. I saw several threads online, including https://www.audizine.com/forum/showt...-High-Flow-Cat from here, about drilling the non-fouler with a 1/2" bit and am curious if the drilling is to allow more exhaust to the sensor or to allow the sensor to sit deeper in the non-fouler. If drilling the non-fouler allows the sensor to sit deeper, it may solve my CEL as well as my exhaust noise.