So I went to a muffler shop here in Boulder Colorado recently and the shop owner told me that if I got a header for my 03 mp5 he could make it street legal, able to pass smog, by drilling a hole near th bend and installing an O2 sensor. True or fales? My guess is false but I hope for true.

 

True.

 

No, not true! The removal of any factory catalytic convertor or other emissions equipment is illegal.

To the OP: you've already got a second 02 sensor near the bend. The only header I know of that does not include a bung for the 2nd sensor is Ractive.
And just screwing the 02 sensor into the bung will not elimate the CEL you are going to throw.


That said, without knowing your local emissions laws, you will probably still pass a sniffer test with a header installed and a CEL fix. You may not pass a visual.

I passed emissions with my header but no visual was done.

 

to make the car road legal you would need to install a catalytic converter down from the header, and install an 02 sensor after that...

although technically removing ANY factory emissions equipment is illegal to begin with

 

Oops ... I was thinking of CEL. My bad guys.

 

I'm so glad alabama doesn't give a crap about the environment.