I saved my bin file from the Pocket Programmer, but when I go to load it into Tuner Cat, a message comes up that says:
"The Selected source file has been modified and the checksum disabled. The Tuner Program can not verify that the proper ECM Definition File is being used. Proceed Anyway?."
Is this normal?? Thanks.

Hmmmm, something tells me the chip you read isn't a factory GM part number. Basically what has happened is that someone has disabled the checksum by placing "AA" in the ECM ID byte. As an example, the ECM ID byte for for an 88 TPI car is $32B and one for a 92 TPI car is $8D. Tunercat needs to see the ID byte to know that the defintion file loaded is the correct one so that's why you got that message. So lets say you had an 88 car ($32B) and someone updated the PROM by burning a bin on it with a $6E bin ID byte (used in 89), then you wouldn't be able to use the def. file from an 88. Another thing that could be is that you have an aftermarket chip that someone has scrambled the info so that no definition file can read correctly. Your best bet is to find the bin your car came with and get it from DIY-EFI FTP site and start from scratch. If you have the factory ecm in the car it should have the BCC on the ECM cover.