reprogrammin ecm

I've got a 1996 firebird with a 3.8 series II engine, auto. I want to have the ecm reprogrammed. I want to eliminate the p1870 transmission trouble code. I've had ed wright reprogram computers for hotrods to my specs but I can't find anyone who does a 3.8. The trans shop has looked at the transmission and they say the computer needs to be reprogrammed by gm or somebody else because the transmission is ok. It only throws the code if you are cruising on the highway and it has no affect on the operation of the transmission after its throw. It appears to be a false code. I've replaced the computer once and it still throws the same code. The trans shop told me their instructions on the code show that on of the first things gm says to do is get the computer reprogrammed. The guy told me that once they get you in the will try to sell you a new transmission. So I just want to find a custom programmer that can stop the computer from throwing the code. I've put 35,000 miles on the tranny while its had this code thrown and it operates fine.