So it's running lean at idle then... Taking the vac line off at idle would richen it up I think. Perhaps it was just setup with an adjustable fuel reg initially...
I would be getting it on a dyno before anything else... Perhaps with an adjustable reg in place so you have some control over mixtures. Otherwise, go back to the stock ecu until you have the Emanage installed.
It's unusual, I would have thought the o2 sensor would have sorted it out, it must be a fair way out...