I have a friend on here who had a 2.8 with an efr 8374 with a 1.0 rear on it, the emap was rising fairly a lot and the turbo speed had been reached, with that setup it made 485kw the wheels. He then swapped the rear out for a 1.45, the emap went down, the power went to near 520kw and had zero noticeable extra lag