When it comes to porting and a rebuild and what not, how much does it relaly matter on what engine you start with? And, why does the 89+ have more power?

all 13b NA are 6 port engines, the port sizes between the 86-88 and 89-91 are the same its only the VDI (variable dynamic intake) thats the major diffrence on the 89-91 enigne that makes the extra few HP. if u are going to port the engine u would need a shorter style intake manifold to take advantage of the port. the stock intake manifolds are tuned to the stock engine.