Emission test: Best bang for buck

[Nexus7]

My 89 with 160k and 3.0L 5-speed is coming up for emission testing in a month. Last time it passed (HC barely OK) and I had put in new plugs, AF, O2 sensor, and EGR. I had run through 2 cans of Chevron Techron fuel injector cleaner also. This time I'm thinking of getting the injector cleaned and cat replaced before I go in. What else should I do so I can pass with flying colors?

Just for context, I think the timing is OK, best I can tell since I can't find the timing marks on the pulley. Idle is pretty bad cold, but I can't find any vac leaks, and don't know what else to look for.

Thanks.

[KimMG]

Make sure air intake is clean.
Change oil.
Check a repair manual for info on timing.
Look at spark plugs. They will tell if running rich.