In this thread youll see the difference between the 2 b18a1 manifolds. They are cast the same, only slight differences in thread location which youll see in the pics. Throttle body and intake ports are the same size so there is no upgrade by swapping either of the two. The fuel rails arent shown but they are the same thing. Only difference is the 90/91 came with obd0 peak hold injectors while the 92/93 had obd1 saturated injectors. Dont mind the hoses, everything is plug and play between the two.

Here are the pics. 1990 manifold on the left, 1993 manifold on the right.

90/91 stamp vs. 92/93 stamp



90/91 front view vs. 92/93 front view

Notice on the 90/91 manifold there is an air boost valve on the plenum. They both have a dapshot diaphram on the throttle body(not shown on the 90/91 manifold cause Im missing one). Its function is to ease instant deceleration. Without it your engine is more likely to jerk when letting off the gas (throttle plate slamming shut).



90/91 rear view vs. 92/93 rear view

Notice the sensor difference. They function the same.



If I missed anything or gave out wrong information let me know and I'll edit the post.