If he's using the DHP scanning software, there are known issues and it is no longer supported. He needs to start using UVScan or get a copy of it. The 97's are kind of wierd when it comes to pcm's, he needs to be making sure the pcm is correct for that year (wiring not changed to use a 98 pcm) and that the files are correct as well. Did he read the current file on the car, then write? Or a whole new file? Did he do a partial write or full? Did he clear fuel trims after every write?