turbo 1nzfe mapping issues

[sportivoecho]

i have a 2005 toyota echo sportivo (australia) which ive turbod using the zage turbo kit, im having a few issues with the mapping. ive had it tuned professionally at a reputable tune shop here in australia but the car cannot get away from a flat spot between 1500-2000rpm right before it builds boost. if we reduce the fuel in that area it gets worse, if we increase it it gets better but we can only increase it so much until the fuel economy goes out the door.

its very strange, its only in that one spot that it has a huge flat spot. i was wondering if anyone has had this issue or could lead me in the right direction?

thanks