I actually passed CA smog with a bad cat a couple years ago, I have a 94 Z28 with a single cat and it was really hollowed/burned away in the center and all melted but it still flowed ok and wasn't clogged up it just had a huge hole in it. My Hydrocarbons were high but well within limits, and that was on a really crappy running stock ECU, 91 octane chevron gas and on a warm day.

With no Cat it's going to be really hard to get those Hydrocarbons down, I've heard of things like rubbing alcohol added to the fuel will help, and I've also heard octane booster helps lower emissions.

Check around for shops that'll help you out, if you look around specially gas stations that smog, they'll usually help you pass.

Good luck!

EDIT: One more thing, do a search on Seafoam on this forum, and look into Seafoam'ing the motor to clean all the deposits out, that's definitely sure to help you out..

 

there was not too many miles since it was rebuilt so it's probably clean, but I've definitely always used seafoam regularly.

well, I'm going to go shop for the 'right' place sometimes next week... as soon as I put back the steering wheel (fixing the signal lever + a key issue)

thanks to everyone for suggestions. I'll post again as it unfolds!

 

I'll be looking forward to your results. I've got smog coming up soon too.