I currently do not have a cat on my car. I plan on getting a hi flow one welded to the downpipe under car. Will this cause a problem and send me back to square one? Also resetting the ecu? Do you mean disconnecting the battery for a while then reconnecting it to make the ecu turn to default?

 

I just had my cat welded in today... thank god. It sounds so much better. You can get cats with 1 bung or 2 already on them.

 

The one I bought doesn't have any. Would it be alright to just weld a bung to the downpipe? I would think it wouldn't matter since all a sensor does is measure oxygen flow. Esp. since I will be using a MIL eliminator for the sensor that measures in the stock cat.