imho you couldnt hurt an injector if you let it soak in the marvel oil for a year.
i have experimented with the same oil to try removing carbon from aluminum pistons and it just wont do the job, matter of fact engine oil did the same results.
i take brake cleaner, use a brass bristle brush and clean the outside of injectors. just be cautious and dont drop the injector and ruin the point on the plunger.
of course i completely dissamble the injectors and completely clean the entire unit,i have a strong solvent(porter t2) to soak all parts.most time there is rust inside.
hope this helps
larry perkins lou ky