[jsveb]

What happens if you try to lean it out? Just a bit at a time. You should be able to hear the change on the engine, also see it on the gunson. If it incr rpm then it was to rich, if. It drops then it was to lean.
There are threads on tuning without a tester all together. They expand more on this. This, I think, will tell you more about your car at idle, and your tester.

Good luck