I'm with Tommy, that optical sensor can make your torque reading all sorts of screwy, does your readout show RPM? take a look at that and see if it's normal, I may guess it was only picking up scattered rpm signals and thought your engine was turning slower than it really was.
years ago I dynoed my dodge at brians tire in poky, I think it was also a dynojet, my HP was 648 but my torque was 4XX and that was at a peak rpm of something like 7000.... I was still VP powered at that time and redlined at around 3800. I think the HP was pretty close but everything else was way out there.