fuel pump/governor kubota?

I've got an old mod. L225DT Kubota tractor.
The last time I worked it, on my first pass I knew it wasn't right, and before I could finish the first run the tractor would't run at full rpms, however it would idle all day if you wanted.
Took a quick look inside the pump and a stretched out starter spring was found and thought to be the culprit. I replaced it and along with the governor spring.
Now then, it's much the same problem. The rpms come up very slowly and I've really no power behind the engine speed. Once the engine gets to temp coming off idle is niegh to impossible. So far as I can tell all the arms, bearings, metering shafts, etc, are free (no binding) at all.
I'm I missing something, or is that stretched out spring an indication of something more serious?
I got to figure something out. We've got more snow coming in day after tomorrow.