my vx just failed smog

[rx7will]

I have a federal civic vx, the one with lean burn. It has 240k on the original engine and transmission. Engine compression is good, tuned up recently. Ignition timing is correct. Engine runs good and does not burn oil. The car already has an replacement catalytic converter installed. I took it apart to fix an exhaust leak and the cat looks good, its not clogged or anything.

I live in San Francisco and we have the enhanced smog. I failed the 25mph test , but it passed the 15mph test easily. I forget to get the print out, but the only thing that it failed on was hc. Mine read around 250, which is gross polluter status. The CO and NOX was was very low. The smog tech thinks it might be a lean miss fire.

So my question is does lean burn kick in at that low of a speed? Usually if the car pass the low speed, it can easily pass the high speed. Is there anything that i can do to turn off the lean burn feature for the smog test. To see if indeed it is a lean missfire caused by the lean burn. We tried to adjust the timing but it did not effect the hc reading. Has anyone else fail on just the high speed hc, but pass everything else?