I can't remember when I used to have the Scangauge in the Corolla - since moved it to my other car - but I seem to recall that it never read zero, but not sure if it was 10+ either.
Assuming you did the calibration routine with the Scangauge?
I remember plugging it in and it seemed to activate pretty quickly, and I set the engine size and fuel tank size, but really didn't do much else. I did set the injector shut-off to 9, rather than 11 or higher because I wasn't sure that it was shutting off the injectors or not when coasting (it was fun for a while watching mileage skyrocket to 250+mpg when I had the cutoff at 11). I need to reread the manual to see if there's anything more I need to do to calibrate it-- it seems like there should be something to tell the injector volume or any number of things, but I suppose it could read some stuff from the ECU.
I haven't tried watching the scanguage while trying to close the throttle more by hand at the throttle body, in case it's binding somewhere and not able to close all the way. I don't clean the TB all that often, but the last time I did I didn't notice enough varnish had built up to prevent the plate from closing fully, as far as I could tell.
I have noticed that with as even a pedal pressure as I could muster, the TPS reading would fluctuate on acceleration somewhat (like jump to 33 and then back down to about 20) and sometimes would read higher than I thought I was applying pressure. I'm not sure if that was a function of the fuel map or maybe I have an ailing TPS. I'm going to try using the XGauge feature to see if I can read the O2 sensors' estimation of the A/F ratio and such.
I haven't tried the SGII in my other vehicle (1995 Previa LE S/C) yet because it wasn't clear that it could detect that it was in a different vehicle and store all the parameters for it to make switching seamless. I didn't want to lose any historical data or mess up how the SGII was 'learning' the Corolla. (Seems like a vehicle tracking/switching feature it would be a true need if it didn't already have it and I haven't discovered it yet.)