All SC's from 89-93 use the same transfer function with the exception that some of the 93's read all the way to 5v whereas the others stop at 4.75v. However, at all increments below that the values are identical which means that there is no difference between an 89 sensor and a 93 sensor. However, on the 94 there is a 15% difference in airflow reading at idle. This is a big difference when the EEC is expected to calculate load based off of those numbers. Adaptive would be able to correct for the 15% but that would take up the vast majority of it's corrective capability. Then there is the issue of the EEC applying learned adaptive to the WOT tables. When you consider that the MAF tables come into re-alignment in the upper airflow ranges, you can see that if the meter is applying a 10-15% correction to them the car is going to go lean by up to that amount.
Of course I may be wrong in all of this, but if so then I'd like someone to explain to me why.