Wow
that is a little hard for me to get used to
Your injector times are longest at idle though, so as you predicted the pressure plays a much larger role.
An injector sanity check might be to look at the injpulses per half second and try and fugure out if it is counting the gap at different rpms or not (watch out for the cold start after pulse).
on the pressure sensor, do you think those "blips" at 0,2,~11,~13 on the red line might be a kind of pwm? does their spacing change with pressure and if so, how?
re: 20 volts, where is the zener?!?
I'm not %100 on which wire you want. I don't quite get how one side of the injector can have higher highs and lower lows than the other, but for now it looks like you found a working signal (1-3.5 is sufficient for off and on to the atmega).
The atmega triggers on at ~2.5 volts and off at ~ 2.2 volts, so I'm not sure that the red line is registering. might need to amplify it or something (ugh)