As I understand, the B&M shift kit raises line pressure across the board, which will work for firmer shifts, but the excess pressure wears the servo seals more than necessary, so you will be paying for a rebuild sooner. The higher pressure also generates more heat and load on the pump. The PCM maintains line pressure just high enough to keep the clutches from slipping, given the torque the engine is making. The Jmod speeds up the clutch and band engagement/disengagement without messing with the line pressure. It is the way to go & worth the extra effort.