Deere 200 clc excavator. 6.8 liter deere engine. 3300 hours came from Hertz and appears to have strict maintenance. We bought it with maybe 3100 hours. Seems to have a flutter out the exhaust, especially when you are away from the machine behind it while it works. Today I was getting substantial blue smoke (some black with it) while under power. I checked the engine and some wet liquid bubbling (guessing it was diesel?)  where the exhaust manifold bolts up to #4 cylinder counting from the engine fan.

My new injector showed up right before dark. I then took the temp gun and scanned the exhaust ports. At an idle they were in the 500's fahrenheit. The middle two though were in the 300's. So maybe I have two bad injectors??? Why would they possibly be bad at this low of hours and is there something I can put in the fuel to maintain them? Do you put a lubricant on the upper or lower injector oring, would oil work? Thanks.