Originally Posted by Dave Henshall
all the sierra and escort cossies have a YB engine, its just the last letter that is different,
ie, 4wd saph without a cat(red top): YBJ
4wd saph with cat(green top): YBG
early escos(blue top): YBT
late escos(silver top): YBP
And a few more codes
YAA - prototype
YBB - prototype and 2wd Sierra
YBC - gp A rally (kit only)
YBD - RS500
YBE - non Ford sales
YBF - Race RS500 (kit only)