I have a 91 6.2 K5 1500 4x4 AUTO trans. Only have had it for 3-4 months. It sat for 3 years straight by previous owner. When first got it Spit/sputtered a lot with very little throttle.

Changed fuel filter and ran "Hot Shots" Diesel cleaner with 1 full tank.

NOW it Starts Excellent and runs much better. Probably around the 2500 RPM range it starts to sputter a little with coughs of blue smoke. You give it more throttle it gets worse. (More coughing and blue smoke.) It is at its worst when it auto shifts to 2nd. (maybe due to more load?) After 15-20 minutes driving it gets better. (Have to get it into higher RPM's to get it to cough and throw blue smoke)

Is this an Injector issue? or something else? Will it get better with time by continuing to drive Or do I just need to do some get some more tune up items.??

Thanks in advance for the input guys!!!