Dont ask me why but my 1989 Bonneville LE has ECC factory installed. And Steeringwheel controls, which sadly dont work anymore. Also has elec drivers seat, pw windows locks, and (he he) a cd deck from a 1997 Bonneville SSEi which, the factory plug was the same (weird eh?)

Thanks for asking this question WJC, I was thinking if I could do the same with my 1990 LE, guess not with my sense. And to add the option debate, the original owner of my car got a few upgrades that were optional like the 15inch diamond spoke wheels, but no ECC

BTW bastard those are my dream wheels, I wish the owner of my car would have order those wheels

ECC isn't that great on these cars. You can't control where the air comes out. Heat is always on the floor, and AC is always through the dash, unless it is on defrost, then all the air blows at the windshield. On the later Bonnevilles, this flaw was overcome and the controls were added to select how the blown air is distributed.
I'd rather have the ability to control the air flow than to have the convenience of maintaining a preset temperature.