Nissan A33 VQ25 Neo engine

I have recently replaced my A33 VQ3.0 brougham engine to A33 VQ25 Neo. Initially, everything looks okay, power and fuel consumption are good till I added in a K2N power booster. Two weeks after adding in the power booster, engine start jerking, less power, high consumption, black smoke and smell of unburnt petrol follow by dirty the spark plugs and lubrication oil. When sending to workshop for computer check, it shows "Fuel temperature". Been to few workshops but none of them can resolve the problem. Can anyone here recommend me a workshop who can solve the problem. I can be contacted 016-2110988. Chris