We've all read that the optional performance exhaust system is good for an extra 5 HP & 5ft. lbs. of torque. My question is where is that extra HP & torque found? Peak RPM, or is it found lower in the RPM band? The same question about the extra torque. Here is a graph I found taken from an early produced Z-51 with the performance exhaust. I could not find one for the base car. I was just curious...