Griesel, another gentleman did a controlled experiment reciently. He kind of proved the marvel oil did dissolve the build up on his injector to some extent. A week sounds about right for an initial soak attempt but watch your ambient temperatures. Chemical reactions slow or stop when too cool. Always best above 70 degrees.
The chances of hurting anything seem very small at this point. Thats with what little knowledge has been aquired to this point. It is also thought that a quart of transmission fluid in the base oil might help but again no recorded results or attempts by members on site to my knowledge. That would also be a really long time related approch if it does help as well. My feeling is the two combined might be of some value.
Still waiting to hear from guys that have rebuilt these engines about how much ring action impairing products where present that they had to clean up.