That was me. Attached are a couple of other scope pictures. The blue and blue/yellow two channel ones are mine. The diagram and the CRT scope annotated one are someone else's. My understanding of what I see is pretty limited, though I understand why there is a spike - the FV, like injectors, is a solenoid, and turning it off creates an inductive spike, like a spark coil does. Porsche's diagnostic plug gets a cleaned up signal from the mini-ECU. I routed both signals to a little box with BNCs so I could look at them in the car.
One of the many things I don't understand is why the on signal, on inexpensive digital scopes, shows up as a bunch of closely spaced up and down traces, while on a CRT they look like a fairly stable voltage level. I understand a little fuzz on a horizontal trace - inexpensive, hardly lab grade, instruments. But the blue lines doing so much of this I don't understand, though maybe it is an artifact of the Sainsmart and some operating frequency. The picture you posted is of an even cheaper scope, with its own small screen, not run through a laptop as with the Sainsmart. It also has the up and down traces, though not so closely spaced.
I tried to modify the system using a PWM generator and two MOSFETs (based on advice from an EE). I ran the FV ground (the ECU grounds the FV) through the MOSFETs. In normal operation one MOSFET passes connects the ECU ground. At WOT, the 3 pin switch on the throttle body tells that MOSFET not to work, and tells the other one to pass the WPM signal instead. I used a CMOS NAND suitably configured to tell the MOSFETS which should be on, and which off.
Alas, it didn't work. I may have wired it up wrong, I may have miswired the DPDT switch which allowed me to change from normal operation to this special WOT operation, and I may just have failed to tell the PWM to output a high enough voltage. And I didn't test with a scope. But the Air/Fuel meter did not change its behavior when I switched the circuit in. Nor did another, simpler switching involving a regular input, as suggested by Andrew, appear to do anything. So probably some goof on my part.
