I'll keep this brief. My neighbor's experience with getting his 96 SE smogged. HC was just a little over the test limit even with the cat hot.
Gutted pre-cats
Y pipe mod
Hi flow aftermarket cat
SVT cat-back
Passed smog check two years ago equipped as above
Did not pass this year
Evidently smog specs are tighter this year
Tried adding stock cat behind hi flow cat - didn't help
At this point he researched and found that he needed an OBD II cat. I have not heard of them before, but he learned that it is more expensive and nore effective. He found a source for one that is speced for use behind an engine up to 5.7 liters so it should flow well and be big enough to clean things up.
Results with this cat by itself and the rest of the exhaust as above - it easly passed with very low readings. HC was down to something like 12.
Engine seems to perform about the same.
