its a 99 2500 silverado with 6.0. Well been fighting this for a while. Replaced the 02 sensors as they were all way appart on readings. Pulled the egr ran a cable up the tubes no blockage. Looked at the pintle cleaned it. Sprayed intake gaskets idle changed so replaced gaskets put replacement wires on kock sensors while I was there. Egr wires tested out to spec. Replaced the maf and air filter. The meter I have shows no numbers on the tps so stuck a new on on it. No difference. Short of buying a scan tool with pid capable settings. Any ideas what I've missed. Forgot changed the tbi gasket looked fine but changed and cleaned bore. Truck runs better now but still sets cel.

 

Possible its a wiring or electrical issue, as the vehicle is 20 years old and, if you live in the rust belt,as your info. says, that makes things go south sooner. Might find a tech to run a Dx on it, then repair yourself. Sometimes I have to use a shop, particularly on a light car, since I don't have a hoist, or enough room or the time to do it myself, but its very rare.