From what I read, the 90-91 Accords came stock with a 2.0 liter engine, and the ex's came with the 2.2 liter engine. There might be a few changes from one to the other. In the 92-93 EX engines, the added a header, a different intake manifold, and a different cam. They look almost identical. 92-93 EX engine was the F22A6 = 135 hp
Just a few little changes, for just a few more horsepower, period.