That is indeed a MAP Clamp, exactly as i described above with 1 difference. On a turbo aplication the ECU will adjust it's boost levels through the ECU controlled Wastegate based off the feedback signal it gets from the MAP Sensor (In that case the TMAP which i assume just means "Turbo Manifold Absolute Pressure"). So in this case the Car boosts 14psi. Car hits 14psi, MAP (TMAP) signal is sent to the ECU that it's at 14psi. ECU then sends out a signal to the Wastegate to open and start dumpng exhaust gas around the turbine.

Now with the clamp they are probably more so rescaling the voltages, so say 14psi sends out a voltage equal to 12 psi, 16psi sends out a voltage more equal to 14psi ect. Now because of this the car will physically boost 16psi before the ECU sees the 14psi boost cutoff at which point it goes and opens the gate to control boost.

So on a turbo car they get the fuel, timing and boost level changes from a Clamp. This is a good and bad thing, good because more boost is more power, but bad because more boost is counterproductive with pulling fuel... So you have to find a happy medium. I don't doubt there claims of 40hp. I've tuned stock SRT-4's to +40hp with simple piggybacks.