Just because you can put in an ECU and put in a gauge, does not allow you to send any signal from the gauge to the ECU, unless it says you can.[/b]
Well, there's two tangos to that song.
The first is what I call "implied consent". For example, the gauge rule states "[g]auges and instruments may be added, replaced, or removed." Nowhere does it state that wiring can be added or modified, nor does it state that sensors can be modified or added. Taken to the extreme letter of the rules, we can add gauges but we can only use factory sensors and wiring, all unmodified. We, of course, infer the implication that we can add sensors and wiring appropriate to the gauges we choose to use.
The other is the "prohibited function clause." So, what's the 'allowed function' of a gauge package? To provide information, correct? Are there any restrictions as to 'how' or 'to whom or what' that information is provided? Is the intended function of the gauge clause to provide
only visual information
only real-time and
only to the driver, thereby making our data aquisition packages illegal? There is nothing in the rules that defines- or even implies - what the intended function of a gauge package is, and there is specifically no restriction to what you can gage, should you choose to.
Therefore, if there is no restriction as to whom, what, or when information is provided by the gauge package, how is it that providing that information to a data aq or ECU - which is specifically allowed - is prohibited? We're back to the George Roffe theorem: "...you bloody well can." Gauging TPS is unorthodox, but it's allowed and, more importantly, unrestricted.
The ECU is open, but currently only within the factory housing and unmodifed wiring harness; gauges that provide information are unrestricted, as are their sensors and wiring; ergo, there are currently no restrictions to wiring that information into the ECU as long as the wiring harness and ECU housing is unmodified. Opening up the housing rule only makes it easier and cheaper to do so.
This very discussion is a great example of why it is good to take the time to get it right.[/b]
No argument there!
On edit:
Remember, the whole reason we're back at this argument after 4 (5?) years is because of unintended consequences. When the ECU rule was opened up 4 (5?) years ago, the intent was to allow re-soldered chips and flash changes. Instead of simply stating that, we tried to get clever and "open" the rule then attempt to restrict it with specifics. I knew the intent, you knew the intent, but the wording of the rule caused it to be doomed from the beginning. I remember when I first heard about "Motec in a box": while standing in pit lane at LRP. Andy told me that the Bimmers were doing this and I was FLOORED. Impressed, but floored.
Look, we've debated this ad nausea for years now, and I think everyone agrees there are two courses of action here: ban modified ECUs, something that virtually everyone agrees is unenforceable, or open 'em up. No matter what you (ITAC "you) work to come up with, the box is already open; you have to recognize that no matter what clever wording you come up with you can't control it. So, Greg's suggestion is to ask the world "if we opened up this rule, what could people do" and see what happens. I think you'll find that there's really nothing that someone can do with an open rule that they cannot do now, yet cheaper and easier. Traction control? Being done. Full engine control mapping, totally ignoring factory inputs such as the MAF sensor? Already there.
So exactly what is it you're trying to stop? Nothing that I can think of right off hand. But, no matter what you do, someone will find a way around it. Time to just open the gates and let the floodwaters in.
Guages are free but if they do a prohibited function in the ECU they too are piggyback sensors 
