My daughter has a 99 Accord LX, with a Vtech 4 cyl. When I go look up parts for it online, they always have two versions of the 4 cyl. listed. The only difference is where it says VIN: F23A1, or VIN: F23A4. Neither of those numbers is in her VIN number. Help me crack the code here.

Edited to add: I know these are the same motors, either with/without the low emission crap, but how do I know which one she has?