Do you get fuel in your oil? And in the cooling system? You should also have some what sweet smelling white smoke if they are bad enough. And im with fox2boost. i would make sure the injectors test out well before you do the cups to kill 2 birds at once. And if they test out good then you can get new cups and use a merchant install kit like this one below. Merchant Automotive 10058 - 01-04 GM LB7 DuramaxLB7 Injector Install Kit
Injectors are all good, I got them replaced about 6 months ago. I'm thinkingn that one of the cups isn't seated right now and its causing coolant to leak. Just recently I noticed a little by the egr cooler, so I think I'm gonna block off or remove the cooler completely and see if this fixes it. Any suggestions???