Had the same problem with a flat spot after getting dyno/mapped. Money down the drain.
After talking to a friend of mine I took it to bhpuk, was sceptical but had to get rid of that flat spot.
Well what can I say, the first map he tried got rid of the spot then he tweaked it some more on the dyno and the results were staggering.
Wish I had gone there in the first place and saved myself 2 ton. Basically it pays to go somewhere that has proven results rather than some muppet with a laptop and ebay maps.
BEFORE

AFTER

the results speak for themselves