when I first went to castle combe with a used pump off a skyline gts-t, she began to lean out above 5k, which according to my dyno graph for the turbo'd stock engine (red line) is round 130bhp
dunno if it was cos the pump was worn or just didn't flow enough for 160bhp (although both the stock and forged engine has been dyno tuned fine with the gts-t pump, so it must be a worn out issue), I upgraded to a walbro 255lph and all was fixed.
went back to combe and mixture was fine.