Need help to identify ECM and what XDF to use

[bmgjet]

Hello,
Mate has gotten a 1988 GM C1500 and its not running the best so I want to do a tune on it for him. Iv got plenty of experience doing Holden so shouldnt be too hard.

Problem I have is the ecu already has a JET chip in it and all the lables have been pulled off the ECM so I cant identify what the original tune should be since that would be my starting point.

The JET chip has
Part# 28814-s
CARB E0#D-243-2

Iv pulled the tune off the chip and tried a few XDF that people said should work for a 88 C1500 but the values look wrong when opened. So im asuming the JET chip uses different layout to the factory one.

Its a Automatic.

Any help would be appreciated.