Calling ecu gurus!

Have an '00 GC8 with an engine swap and some extras (EJ207/VF34/yellow tops/TBE/AVC-R) but running on the standard Y7 '00 ecu. Runs pretty (quite) rich and was looking to drop in a 99 STI ecu short term as the internet indicates they run a little leaner and harder

Picked up an ECU that is supposedly from a 99 STI but just having a little trouble verifying that's the case before installing and swapping wires around. Numbers are:

E3
22611 AE801
A18-000 D1E (8Z15)

Depending on the forum you browse, eBay listing you view and person you talk to it changes. There's a nice listing on this forum that lays-out the serials and engine configurations but the E3 doesn't appear to be on there unfortunately.

Is there a sure-fire way to identify whether or not the ecu is STI (and/or AUDM/JDM origin)? Serial numbers/board ID/pin-out test...? Little hesitant to change any wiring or swap and run before confirming

Cheers!