The normal resting current is about 10ma
This is my 1987 924S with a cheap Harbor Freight multimeter. 8.65ma.
Start the meter at 10A and move the dial down to avoid burning out your meter.
With the meter in series with the positive cable and the positive battery post, start removing one fuse at a time to see which one will drop the amp draw.
Usual culprits are door light switches, glove box light switch, emergency brake handle switch, and the BIG one-----short in your radio/CD/video whatever. Mine was in the radio.
GL
John_AZ
1988 924S + 1987 924S