Using a short length of 1/8 inch braided cable mounted in a drill, I managed to open the EGR passage to one of the openings in the intake manifold just below the carb. Compressed air blown into the EGR port blows out the rear opening just below the carb. Tomorrow I will open up the other passage, and try to get as much gunk out of each as possible. And then, when the mood strikes me, with my unclogged EGR ports, and my shiny new coolant system, I will go pass smog with my stretched timing chain. Thanks to all!
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Tx for welcome back! Covid related computer tech difficulties , only have phone access âŠawkward to doâŠshall try to check in time to timeâŠbyeâŠhope jack s egr port cleaning does trick
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Thank you very much, George. I remember you from times past when you replied to my requests for help. As I just posted, I managed to open one EGR to intake passage and will open the other tomorrow. Your suggestion was truly the answer to my prayers! 
Jack
Youâre the one who adamantly shot down the initial suggestion as something you had already checked and dismissed. People trusted your assessment and went on to the next likely suspect. Donât act like a jerk now that itâs back to something you said it couldnât beâŠ
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I stand as accused⊠and proud of it!
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We missed you. You ok?
Yeah, totally ok, just some internet tech difficulties. Tx 4 concern. Hope all regulars here also rolling w the pu nches and doing ok. Took me 45 minutes to figure out how to type an underscore characterâŠ
Lol
E
Lol, welcome back!!
No one suggested it until George showed up.
I asked if the EGR valve was operating and you stated that it was thoroughly tested for operation. Applying vacuum to the EGR valve to prove operation is a primary test. After that the the discussion took a left turn into stretched timing chains (not worn timing chains?)
Ahem . . .
recheck your messages . . . hint, hint
5 days before George mentioned it
Because in your first post you knew best and proclaimed the following:
How are we supposed to know you actually didnât know as much as you implied you did? At least until it circled back to what should have been reasonably obvious to someone that was capable of being âabsolutely certainââŠ
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Hereâs what I wrote: âThe EGR valve is not clogged, neither are the passages to the intake manifold and the exhaust manifold, if I can believe the wire that I poked into both ports, which extended to under the carb, and 6 inches or more into the exhaust manifold.â
Well, as it turned out, I couldnât believe the wire that I poked into the intake manifold. Itâs not like I was trying to deceive anyone.
Never give up!!!
Congrats on the pass!
Judging from the elevated O2, very low CO, and marginal HC, I believe itâs running a little lean.
Did you return the timing to spec?
Itâll run stronger if itâs not retarded.
From previous failed tests that is what I thought also, but when I riched up the mix the HCs went higher, so I leaned it out. Thatâs when it passed. The smog pump system is working and passages are clear, so that might contribute to higher O2 out the tailpipe. CO is always very low, sometimes zero ppm, even when I richen up the mix considerably. No comprendo.
Now why would I tamper with the timing after I passed? I surely do not want to bring the Smog Police down on my head 
But if I were to do such a thing, why stop at spec? It would run even better a few degrees advanced from spec. But I would never do such a thing. 
Congratulations!
You barely passed, as far as HC goes
What usually happens . . . do you usually only pass by the skin of your teeth?
But you donât have to worry for 2 more years, in any case
A guy in my neighborhood has a 1st generation Dakota, looks to be about the same vintage as, yours.
Itâs got the aerodynamic headlamps, versus sealed beams, so I assume itâs not base model. Itâs always been registered, so I assume itâs been passing smog tests all these years
What happened the first test after you got the replacement cat . . . did it pass with flying colors, including hc? Or was it borderline even with the brand new cat?
I didnât consider that it might have an air pump.
That will certainly add some O2 to the exhaust.
And youâd never, ever consider a re-curved distributor. 
Not on HCs. Those are usually pretty comfortable, often less than average. NOx has always been a problem. But that was caused by two problems that I rectified this time after exhaustive testing. 1. Increasingly clogged EGR intake manifold passages, which finally closed up altogether. 2. The stock EGR valve which does not provide enough EGR under dyno test conditions, 15mph at 50% load and 25mph at 25% load. I installed a spring assist which allows valve to open more under these low vacuum conditions, and that made a huge difference. CO has never been a problem, sometimes zero ppm.
The part that has me stumped is that the last time I had a dyno test in 2016, the HCs read 48 and 41 for 15mph and 25mph respectively, and that was with the same main jets in place when I kept failing this time around on both HCs and NOx. It was only when I leaned out the mix with smaller jets that it passed.
An interesting side note. When I took the test in 2006, at a different facility, O2 measured 25%! According to this measurement, not only was the engine not burning O2, it was created new O2. So machine calibration must be a factor in test results. This is the first time I have taken the truck this particular shop. When I failed the first time at this new shop, I didnât make any changes since I passed the dyno test in 2016.
Your neighborâs 1st gen Dak, if not an 87, has a throttle body fuel injector, which is computer controlled. 87s came with a 6280 Holley carb equipped with an O2 sensor-controlled mixture control solenoid, and when that went south there were no new replacements available at the auto parts stores. In 2008 I modified a Holley 2280 to work with this system. It is basically the same carb as the 6280, but without the air/fuel solenoid. It has always given very good HC and CO readings. Up until this year the problem has only been NOx, which I finally solved.
I have a pair of jets that are one size smaller than those currently installed. When I recuperate from the last two months of dealing with this I want to install them and take the truck back to the same shop for a tailpipe reading to see if HCs go up or down, and to see how it takes the California foothill roads going from the valley to about 2,500 feet. While all this is still fresh in my mind I want to see if I can improve the HCs.
Not much change in HCs from before and after new cat installed. They have never been a problem until this year. Climate here in CA Central Valley is much hotter and drier than SF Bay Area where all previous texts took place. Perhaps that affects HC readings.