what were your readings?
A couple suggestions I would make about emissions tests... I had a hard time a few years ago but figured it out.... big thing is make sure the basics are covered... do a oil change... make sure your plug wires are good... make sure you have decent plugs gapped right... check your cap and rotor.. and also make sure your air filter is clean... I haven't ever changed my fuel filter but have been told that it is important.... another big thing is to make sure it is warm before it goes in.... have made that mistake myself... sometimes at places around here like canadian tire they will take your keys and the car will sit in the parking lot for sometimes up to an hour and will cool down. then they take it in and it fails... one thing I did was take it for a good run on the highway... then drive it to wherever your getting it tested... go give them the keys or whatever.. but if you have a extra set of keys go out to the parking lot and keep her running... till right before she goes in.. that honestly helps!!!! Other than that.... my guess would be o2 sensors pcv or egr valve... do you have a smog pump hooked up??? check your engine error codes too!! engine off and engine on codes.. oh and while your at it throw a bottle of guarantee to pass in there....