I just went through a fairly nightmarish smog-check on my '94. Basically, it didn't pass, and they didn't know why. Ultimately it was determined that my catalytic converter was kaput, and needed to be replaced. Then it took another week to get the part. Altogether my car was in the shop for about 10 days.
The good news is that the dealer<sup>1</sup> gave me a loaner Integra for the duration, and finagled a warranty repair for the lot, so it didn't cost me a dime (beyond the usual check/certificate charge).
-Bob ('94 #496)
1. Los Gatos Acura