"If your ecu is bad the chip can be replaced easily, and alot cheaper than buying a rebuilt unit."

I've got a 556 that malfunctioned (let idle and fuel-air balance get out of whack). I fould a 561 that works fine, but I know about the bad rep the 561 has.

I still have the 556. How do I find out whether it has a bad chip--and if it does, where do I buy a replacement chip?

Thanks for any help you can provide.

Doug Harvey