I PUT DE-CAT FRONT PIPE ON, AND SINCE THEN WHEN I PUT MY FOOT DOWN, ENGINE CUTS OUT AND RUNS OK! BUT THEN CUTS OUT EVERY TIME I CHANGE GEAR UNDER LOAD. ANY IDEAS WELCOME PLEASE.

 

Fuel cut maybe if boost has risen slightly with decat on???????

 

Overboost? Its freezing today and it does increase your boost.

 

fit a dawes davice so you can set the boost. you will need a gauge if you haven't got one to read what you have set at.
I'm not sure of the fuel cut on a WRX (maybe 14.7 psi) so if you set it at 12 psi if it rises the fuel shouldn'd cut in.
This is only a sugestion.