I wouldn't say a Subaru specialist, but I've seen Subies at the shop with other JDMs like Nissan's and Mitsubishi's.

Definitely in that rev range. If I don't take off with revs over 1k rpm I will notice the flat spot. Also when I am coming to a slow in second gear, say to go over speed bumps, if the revs go down below 1k and I am stepping on gas again I will notice the flat spot.

Tuner said he has added more fuel in that range, turned off o2 sensor, etc but cannot figure out what the issue is.