Basically when the engine is cold or should I say it's far worse when cold.
Between 2 and 3.5k under steady accelration, I get very bad surging.

As if the boost or fueling is is going up and down.

Now i'm a mechanic but i've not got any software to carry out
some diagnostics, I know there isn't a single fault via the flashes on the dash.

Already had the boost solenoid off and cleaned it out, not an ounce of dirt in it.

Been told by a very renound company on here it's down to the 200 cell cat, a full ninja turbo back system and the fact that it's not remapped for this.

Any other possibilities other than a £600 remap?

 

They are right.

A £600 remap isnt the only option