1992 BMW 320 NO POWER-VERY HIGH REVS

hI I own a Bmw 3 series.autoshift 2 litre engine.Over the past year the fuel consumption has deteriorated.I experience very high revs before the gears change.Also as much as it revs well into 6or 7000 the car just does not move.Spent money on having the gear box overhauled and the problem is still there.the idle when parked is steady at 1000.Once you move it revs to 6 before it reluctantly shifts and does not accelerate.Can you help please