I had a R-22 system replaced with a Puron system about 6 weeks ago.
System works ok, but my TIF RX-1A leak detector indicates a leak at the
condensate line T connection near the evaporator coil. When I called
the contractor a couple of weeks ago, he said that it was probably just
refrigerant oil residue in the drip tubes.

Does this sound likely? Could this just be residue from the old system,
which did have an evaporator leak?