JDuncan said:I would suspect that the 5th/6th ports are't activating correcty. On the S4's they are activated by exhaust pressure IIRC. If it has aftermarket exhaust then you might want to check to make sure provisions were made to provide that activation.
doh, you're right, i forgot S4's valves are exhaust pressure activated, the S5's uses a bunch of vaccuum tubes to do that.