what could this be ??

i bought this 02 wrx with turbo xs stage 4 from a friend. not every time but somtimes at full throttle after 5k the engine light flashes and it kinda gives out, feels like its being restricted of fuel or somth. i thought about fuel cut.. but doent the Utech have a defender (pretty sure it does). or maybe its my clutch about to die on me.(pretty likly)
i just need some good thoughts on what it could be :eek7:

If your clutch was about to die, the revs would peak slightly at every gear change before the clutch would actually completely engage, this would be due to the slippage.