Inorganic salts may cause liner and column clogging. If your analyte is volatile, alternately you can use GC headspace technique were salt does not interfere your analysis.

If you use an injector liner designed to capture non-volatile components, such as a glass wool packed injector, the salts will be capture in the liner. The liner will need to be replaced more often but this is not a significant issue. Depending upon the quantity of salt injected, there may or may not be a significant difference in the rate of replacement. Peak widths and peak tailing would likely be indicators of the need to change the liners.

Better not try this , think about some derivatization or something, because you definetely will poison your column and clogg it.

You need to make sure that the borohydride is completely oxidized - injecting borohydride into your injector port is a really, really bad idea. As long as you have quenched the borohydride then you effectively have alcohols in solution, which you can probably direct inject. Depending upon the MW of the alcohols I'd probably recommend that you use headspace since you'll eliminate issue with the sample matrix.