One of the catalytic converter's biggest shortcomings is that it only works at a fairly high temperature. When you start your car cold, the catalytic converter does almost nothing to reduce the pollution in your exhaust. This is an important note when taking your car for a complience test - make sure that it has had a good steady run to heat up the Cats to working temperature or you could fail your emissions test.
anyway..u can de-cat ur car if u want...but if everyone did this the world would be a much shitter place...do ur kids a favor and buy a decent hi-flo as suggested and produce less pollution.