original ECU for GSR can be re-programed if u rechipped or piggy back it. for example, J5 from Matspeed, u can put in that chip into the 93T ECU and re-program it or others brand like e-manage. IMHO, if u wuld lke to go for chip, rather save more and get EMS. better and more thing to tune.
hope i explain the things u wanted. the link u post up lazy to read.