To turn off the custom Ghostscript parameters, rename the registry entries (GSPDFOptions or GSImageOptions). For example, renaming GSPDFOptions to _GSPDFOptions forces the PostScript (PS) to Portable Document Format (PDF) routine to use the default parameters.
Alternately, the registry names can be kept intact, but their values can be empty. Even though the Ghostscript conversion routine finds the registry entry, it still uses the default parameters if the entry is empty.