Any smog experts out there?

Exhaust leaks will affect your post cat reading, but post cat o2 only meters cat efficiency...the pre cat o2 is what the computer uses for af metering...that one bounces at idle normally then steadies as you accelerate , climbing to rich at wot..900 something, both should 'under wot'. If you have an exhaust leak.. deceleration will show lean spikes on the post cat O2 sensor...but it won't correct for it..only the pre cat o2 will..and the pre is already bouncing when letting off by then. Watch the live data. If there is a exh leak...your post will be lively instead of steady like it should be from sensing too much oxygen.

One thing you always want to do before you go to a smog test is get on the freeway and drive it for 5 minutes and get that catalytic converter nice and hot get those O2 sensors nice and hot and warmed up. You also dont want to run OLD GAS. Octane boost helps old gas.
does this thing idle smoothly?
No chance of a plug wire loose?

Aside from those obvious things you could also have a bad injector/leaking injector o ring.

But I've gone through the California sniffer with a bad plenum gasket before and passed. I've passed with a leaky injector o-ring before. My truck has no EGR but has 314,000 miles on the bottom.