I've used AM28F010 (they are EEPROM)chips on my T5 and I can still flash them.
About the EEPROM out of the trionic I'm not so sure it will work.Fine electronic components of that type are very resistance sensitive and I don't know if the wires you will use won't mess with the signals.Technicly I think it is possible but also very hard to be done.
As far as I know the ecu only saves adaption data on the ram memory.And logging is done by downloading realtime feedback from all sensors, the ecu doesen't log data it only adapts a little and saves the adaption data.
I might be wrong, please correct me if so.
And last but not least, WHY on earth would you want to make your own engine control?What software is going to control it and what software will you use to modify it? I would understand it if T5suite didn't exist and you had to use some crappy OEM tuning software like ECM or so.The guys here have worked so hard so that everyone with very basic idea of how an engine works could do whatever he wants with it.
If you want so much a different ecu buy a megasquirt.It has everything you need.
Saab 9000 97' 2.0 T, TD 04-19t hybrid turbo, 3bar mapsensor, big intercooler, sports air filter, siemens deka 630cc injectors, 3" exhaust system.