Originally Posted by Kolyan2k
Why wouldn't it pass emission... its just a flap, even if you remove cat completely it will still pass. It has nothing to do with passing state inspections. Every car manufacture is trying to make their cars greener
Are you sure you understand the difference between a muffler and a catalytic converter (cat) ? If you remove the cat, you will NOT pass emission test, NOx will be out the window and will fail you (not all states have emission test, though). This is a box that contains chemicals, if it gets abused (overhead, contamination from coolant/oil additive), it gets damaged and needs to be changed for much $$$.
Now it seems the flap has nothing to do with the cat (heating it or not) and that running the cat cold for extended period of time has no effect on it (checked myself since I got ironic answers here... ).