Rich,
I'll second Jim's advice to follow JK solution. Your dealer techs see a small subset of Trucks sold in your area. So they may have see a few that are having issues like you are seeing.
In JK's case. His business is like a lightning rod for problem trucks. He sees trucks from all over the country that seek him out to cure this same problem.
Looking at the cost of his suggested cure isn't that bad compared to an injector replacement or truck replacement. Call JK and enjoy life!
dave
Dave, N9LOV
Member #242
Dave's Diesels:
Sold June, 07 '82 1/2 ton 4X4;340k miles
'97 2 Dr Tahoe, Intercooled,
Kennedy ECM, 4" Exhaust
'02 GMC