need help on 05 turbo,at 15771.miles factory replace turbo. the turbo makinga noise like fan blade hitting raditor.history of tr. at 6000miles had k/n filter,edge system and 5'exhaust install.nosie came back app. at 48000miles. at 52050miles had heads,oil cooler inner,injectors and head studs install .egr valve replacement plus replace edge system with a 45hp chip. mechanic check turbo and said it was ok, turbo still makes the noise. this only happen when accelerating and let off not all the time, mechanic went for a ride and heard the noise. he said it was due to the chip and the turbo pushing air back throuh air intake. he said he could remove chip and engine light would stay on and recive no engine code also said chev. and dodge was as bad. i don't understand the problem since the the factory replacement turbo noise was gone until 48000 miles any helpwould ease my mind since i invest a big repair bill. mechanic is going to remove turbo for another inspection.