firmware password lost OS X EL Capitan macbookpro

I cannot reset firmware password on MacBook Pro5,5 mid 2009, El Capitan OS X 10.11.6. Computer had virus and Cmd R invokes firmware password as well as safe mode. Cannot do traditional fresh install of El Capitan. Tried everything and will travel to Apple Store where they will do a reset with proprietary tool unless someone might have a solution. Thank you.