TPS voltage should be at least 4.8 volts at WOT. If not TPS is bad or out of adjustment. No dead spots should be present, and watch to make sure it does not go up to 5.0V and drop back down while opening the T/B to WOT.
I too have seen these and assume they are just some sort of "gaget" designed to fool the EEC by giving a non-linear increase to the TPS voltage.
They claim to limiting voltage to a 5.00 max. and indicate WOT earlier. Thus making the EEC believe you are at WOT earlier and putting the EEC in Open loop, not good in my opinion. Reminds me of the early days of computer engine managment systems when people would drill holes in the exhaust upstreem of the O2 sensor, believing this would fool the computer into "thinking" the engine was lean and thus sending more fuel to the engine.
May sound good in someones mind, but deosn't work in practice... will not go into the why.