I wouldn't rev the Car past 8k anyway, not untill you buid the motor up. If you are going to replace the Ecu I would go with a rTek, website (
www.pocketlogger.com ). You could send your Ecu and you can have it upgraded, or find one that alright has it done.
N350 - 89 NA California
N351 - 89 NA
N352 - 89 Vert California
N353 - 89 Vert
N370 - 89 Turbo
those are all S5 (89-92) ecus. Once you have a rTek you can tune your car with a Palm OS PDA, they have a list on the website above. I haven't found any difference between a manual and Auto Ecu, however I maybe wrong.
however is the car a Coupe or a Vert?