Not much progress since we talked last. I will attack it this weekend. I have been tied up with new sports season starting for my kids and lots of meetings.

My plan:

As you suggested, get a speedo cable and attach a small circular brush to it somehow. Using a vacuum cleaner, apply suction to the EGR pipe leading to the intake manifold while running the spinning brush down the pipe. I am concerned about the amount of carbon buildup that I see inside the pipe. And as you said the real heavy stuff is probably at the far end of the pipe. I have a spare 5.6 liter engine sitting around here so I will practice on that first. I have about a week on the retest time so there is some financial incentive to get it done this weekend. Also going to try to feed the engine some of that GM "top end cleaner".

In the meantime I have located a cat at a cost of $415 shipping included in case the worst happens. Dealer wanted $2000 for the same part.

Do you think with my NOx numbers being so high that the non-functional EGR would account for that. Or do you think that the cat is the primary cause?

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I got too many cars!! Insurance eats me alive. Dave

78 Corvette Stingray - 3k
82 242 Turbo Volvo - Manual - 270k
86 300e 5 speed manual - 210k
87 420sel - 240k
89 560sl - 78k
91 420sel - 205k
91 560sel - 85k
94 GMC Suburban - 90k
97 Harley Davidson Heritage Softail - 25k
00 GMC Silverado 1 ton 30k