You appear to be pretty far out. It may indeed be the catalytic converter that needs replacement.
However, if you want to try again, I usually tell my friends that live in the socialist zones of the country the following:
1) Change oil immediately before the test. Use an additive such as STP oil treatment that further thickens the oil. This sharply reduces burning oil.
2) Start using premium gas for a tank or two before the test. Premium is cleaner and the refiners take better care in handling it. Regular is used to flush storage tanks out when they're being cleaned.
3) New spark plugs was a good suggestion.
4) Try to make sure there are no loose vacuum hoses that would mess up the fuel mixture by sucking in air.
Like other people are saying, you probably are looking at something more expensive to fix. But the test may be worth another try if the oil was old, the spark plugs are old, the EGR valve is clogged, and the fuel is dirty.
Good Luck -