To elaborate on txhatch's post,

90-91 B18A1 = 130hp
92-93 B18A1 = 140hp
94-9? B18B1 = 142hp
9?-01 B18B1 = 140hp

I think the horsepwer drop occured in 96 with the introduction of the OBD-2 computer system, but I am not 100% sure. It is perhaps also better to say the B18A1 is from "non GS-R" 90-93 Integras, for the GS used it and was far from a base model. Also, from my understanding, the PR4 head castings are identical, but the cams and manifolds vary by year.