Ok so I have a 4.75 forged short block with cnced port and polished heads with stock cams with 20 degree phase limiters and stock valves etc. The power adder is a turbo thats .68 a/r hot and .70 a/r cold. The boost was set at 15 p.s.i and only made 421 hp and 500 torque at 4200 rpm then falls off. The tuner was stumped he tryed everything he could think of during 15 different pulls and it didnt get better. The only thing he saw wrong was that he set both cams to retard between 9-14 and one cam did that and the other was all over the place. Could this be do to a bad cam position sensor or the vct oil control solenoid? And does anyone know if this could hurt the hp that bad.