read along for those who are curious..
My E38 was in a recovery of sorts, I had tried writing an incompatible OS(yes I now know better).. gm sps could see the ecu bit failed with a 74 negative response code and failed programming every time..
logging the programming session and comparing it against a good sps session showed what was failing..
My download bootloader request was failing with a code 22, figured out was a security issue(thanks to the documents here!!), my ecu was always unlocked.. When sending it a 2701 seed request it always came back with an unlocked status, then it wrote the 34 bootloader request but failed so sps gave up..
I tried copying this section of code with some real shitty code and used an elm327 and found out if I sent a 2702 0000(any key worked) AFTER the 2701 even though it was already unlocked the next 34 bootloader request got the correct response, woohoo!!!
For actual reprogramming I simply set up a terminal program with an elm327 and a Y cable and an MDI using sps programming to inject the 2702 0000 command when I saw the 2701 command.. I had tried to time it perfectly but gave up and just started tapping/sending the command about every half second when it started changing programming mode.. I know it's dirty as hell but it worked!!!
Looking forward to how this site develops, definitely owe some thanks already!!!