Our old D7 is a farm dozer that we've had for about 10 years I guess. We use it spring through fall. For a few years before that we had a D6 9U that was a good old machine. The D7 is idling a little rough these days, and I was curious if there was an injector that needed spiffed up. I know on our farm tractors the injectors can be shimmed up. Is it the same for the D7? Is that the most likely culprit? Is it pretty straight forward in pulling them out, or is there something I should be aware of or a special tool I will need? Seems like the old girl smooths out some once I open her up. Although she will let out a puff of smoke at times, as though on one cylinder. Thanks for the help.