What rickbass said.
Interesting that you bought the EB in the first place! The reason people buy them, as I've heard, is precisely that incredible brightness. The strings you got on the bass when you bought it MUST have been pretty gunky by the time you got to it, to have managed to conceal that brightness from you.
You may have to consider flatwounds... or trading in the Stingray on a used Gibson EB-0!

But if you're going to put the old strings back on, then don't bother cleaning them.