i guess every car is different. im gonna do that steel wool thing though to try to prevent it from happening.

Maybe it depends on the car but I think as long as you have the extended bungs, make sure there are no leaks and O2 sensors are tight, you shouldn't have a problem.

I started out with Berk high flow cats for about 7000 miles and I now have the CNT resonated test pipes. Not a CEL from either set. I've had the RTP's for only about 100 miles so far but no issues and I am very impressed with the quality for the price.

You can purchase the vibrant J bungs they screw on and havethey same effect as the ones with the J bend

That's definitely a cheaper option. It'll allow you to buy a cheap test pipe and just weld the bung on. Good find!

You dont have to weld they screw right in..
Heres a link that might help for u guys my cars no CEL light

Vibrant Oxygen Sensor Defouler - Universal Exhaust Items

which test pipe are you running? and does ur o2 sensor screw into that j bung?