i ran into a similar problem when tuning a 2.0 with 272 cams, 49lb wheel, fmic, 850cc, fp
the usually goodies to support a 49lb turbo.
had to tweak the maf table to get the stumble/hesitation to go away.
which cam sprockets did you use?
but the timing issue is odd. the factory timing for ej257 closer to 20~22