well my cats on my 83 stang are on, But the inner filters are cutted out, when they do a visiual they see the cats there, it passes that. Like I say I used methol hydrate every year though emission tests worked for me, When methol hydrate burns it clear no carbon is left, Ive done alot of tests. emission tests are just another form of squeezing money outta people that own cars (Basic terms CASH GRAB). Of course if youre cars engine is tried out, Barely runs their is a possiblity it wont pass, For a good running car I see no problem.