Help; failed CA smog test. High NO

It's that time of the year again... the dreaded smog test.

The last time I tested was a couple years ago and I barely passed. I'll post those numbers when I find them.

However, I went to the smog guys a couple of times this week (utilizing the free retest). No go. Here are my numbers:

1st test (drove 20 miles on freeway before taking test):
/////////// 15mph // 25mph
RPM ////// 1716 // 1698
CO (mea) 15.1 // 14.9
O2 (mea) 0.1 // 0.2
HC (max) 61 // 35
HC (mea) 26 // 19
CO (max) 0.34 // 0.47
CO (mea) 0.15 // 0.21
NO (max) 486 // 502
NO (mea) 626 // 658

2nd test (drove 7 miles on surface road at 45mph max before test, idle 5 mins):
/////////// 15mph // 25mph
RPM////// 1929 // 1781
CO (mea) 14.8 // 14.4
O2 (mea) 0.0 // 0.0
HC (max) 61 // 35
HC (mea) 3 // 1
CO (max) 0.34 // 0.47
CO (mea) 0.01 // 0.01
NO (max) 486 // 502
NO (mea) 909 // 617

I was so close on the 1st one, I thought, after filling it with new gas (always premium), I should pass. I thought way wrong. When I drove there, the car was fine. Then after idling for 5 mins and the guy drove it up to the dyno, the idle started acting a little funny and revved up and down for a sec. It's happened before, but always randomly (like this time). I've read cleaning the ICV may help this problem.

I've read up for the past couple hours on what high NO means and it seems like I"m stuck possibly looking at a new CAT. I've read differing opinions about the O2 sensor. I haven't changed my spark plugs in about 4 years (though only driven <15k miles in 4 years).

Before taking the 1st test, I did do:
1. change oil (Mobil 1 5/30)
2. clean the throttle body w/ toothbrush and TB cleaner
3. 1 bottle of Lucas fuel injector cleaner

Any thoughts on what I should do to attempt to pass smog? From what I've read on tonight, cheap things might be to change the O2 sensor (Ford goes for $35 or so) and spark plugs at $4/each or something. I'll definitely clean out the ICV this weekend. I saw the DIY and it's hopefully doable.

Some folks have mentioned checking the EGR valve. I'm not sure where it is and not sure how difficult it may be to replace.

Thanks in advance for any insights into this problem and helping me get through the dreaded smog test this year.

Cheers