The O2 sensors would probably behave differently and throw some sort of fault code I would assume... So whether or not that would be a engine light or not is up for debate or go into limp mode or hesitate at certain RPM's.

I think that's the biggest issue the O2 sensors and what half of the stage 2 map is letting the Ecu know that it's free flowing

 

Emin that's a big gamble. Not worth it unless u have an expert who can reprogram ECU I think!

 

Car will almost certainly flash up a check engine light as the ecu is programmed with a catalytic converter in place.if you then remove this, it will require mapping to account for the extra gas flow.

 

In my experience it may just flag a warning light or it may also provoke limp. And on a trip, the limp mode is painful cos you have only half of the cars power! This happened to me half way from Italy heading thro France to the UK so I had about 700km to cover, not fun!

 

No i got down pipes and x pipe no flags no warnings at all