"The problem I'm now having is that it has a rough idle when the throttle lever is all the way back. If I bump it up a little then is smooths out. I've used another 7100 a couple of years ago and don't remember it idling rough. "
When your throttle is all the way back, do you know what RPM you're turning?
My Deere 670 idles a bit rough if the engine is under 1000 RPM's. I just bump it up to around 1200 or so. A little higher idling RPM is easier on the bearings, by the way.
Since none of us can know how rough your engine is actually idling, and you are being somewhat subjective about the issue (as we all would be...trying to troubleshoot without personal experience with your tractor) it's difficult to determine if you've a real problem, or perceived problem..
Since you went thru some tankfuls of fuel with a conditioner, maybe dirty fuel isn't the issue. You could have a partially blocked injector or an injector that went bad (one of the tests a mechanic does on injectors is observe the spray pattern).
If you have the manual for your tractor, does it specifiy an idling RPM, by the way?
