Two things seem apparent:
1) There seems to be some sort of positional smoothing going on. Did you start with a preset? Check the emitter position accuracy setting (don’t remember the exact name of the property); the options are something like 1, 1/10 and precise.
2) If the path and reference image are 2D and you have a 3D camera, any movement of that camera will offset the path. You can try creating a new camera or moving the existing one if this is the case.
Kalleheikki Kannisto
Senior Graphic Designer