Tapping into TCU wires with a digital multimeter?

I'm starting to get more serious (and hardcore) about some tricks that I'd like to perform on the TCU... The full thread can be found here .

To keep things simple (so that you don't have to read that huge thread), I want to modify the way that the TCU reads RPM information, thusly making it believe that the engine has a different RPM value than in reality. Since the TCU reads RPMs as a variable voltage amount, and then transforms it into an RPM value, I just need to change the voltage that the TCU "sees" at one particular wire pin. This is very simple electronics... The voltage just needs to be lifted or dropped 7% - 8%

The ultimate goal is for the engine to be at redline (7000 RPM), but for the TCU to think that the engine is at 6500. This will allow higher revving (given that the ECU's rev limiter has been modified, via something such as the ECUtune Stage 1 chip), and should also keep the transmission in each gear a little longer, whether you're redlining or not.

Anywho, I need to find a way to tap into the TCU wires with a digital multimeter, and drive the car around. I need to see if the voltage varies from 0 - 12, from 12 - ground, or if it has some other voltage quantity. This cannot be done with the leads that are provided with most multimeters, as I can't physically hold them to the TCU wires while driving the car. An ideal setup would be for the positive lead to hookup to TCU wire, and the negative to hookup to ground... I just need some neat idea of having the multimeter's leads stay there, allowing me to drive. I am open to purchasing a new set of multimeter leads.

Obviously, I am also attempting to leave the TCU wires unharmed.

I'm going to try reading some of the service manual stuff, to see if this voltage amount is documented anywhere.

I know there are some electronics wiz guys on this network (you know who you are), so help me out please!