impreza dies at 4000 rpm!!

Hi again, my friend told me his problem with his impreza turbo (r plate 1999)his problem is this; the car starts and runs fine up until 4000 revs
then as he says engine dies/looses power/gurgles but ok again when below 4k revs!! has anybody had this fault as he doesnt want to go to mr subaru for diagnostic as santa is not far away!! thanks in advance!!
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Fuel Filter...... Fuel pump/regulator

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