And this is why whenever I sold good A4000, I asked some high money not comparable to some junk on ebay, where battery was not mainted properly... if battery leaked and ate through the pcb, then the person just cleaned the surface its kinda of too late - looks ok to the eye but board will fail. In your case, don't sweat on it, just populate the Warp Engine as its way faster and can get more memory on it.
A leaking battery can cause all sorts of problems. Even if the battery has been removed, if the board hasn't been cleaned properly the alkali can sit and eat through the board slowly over time and then show up. Try removing all the memory from the mother board and then fill one memory slot at a time. Start with the slot furthest from the battery.
Putting the memory on the Warp engine as Tone suggests is a good idea as it will give you a speed boost.
Weed
