Try to get more info about the test.  In Chicago they use a dyno for
older vehicles, but they don't test for NOx.  My '80 used to pass with
no problem and its cat was hollow.
   Traditional dry-gas is methyl alcohol.  It can be bad for some parts
of the fuel system, so I wouldn't leave it in there very long.
   Change the oil. Check for vacuum and exhaust leaks.  Be sure the air
filter is clean or remove the element temporarily.  Don't let them put
the front wheels on the dyno like they did with mine once.  :-)
   Good luck,
Larry A.

Christopher Gronski wrote:
> 48 hours the test. I dont necesariy have to pass but  get complicated
> if I don't. My cat is in place with the o2 sensor, but apparently is
> hollow. My exhaust is a new (three week old) S&S header system.
>
> Chris
>
> On 8/18/05, Dennis Haynes <dhaynes@optonline.net> wrote:
>
>>Is that 48 hours to take a test or do you have to pass it? If you are
>>getting a dyno test, most likely you will need the cat for the NOx. Part
>>of the test.
>>
>>Dennis