Most are aware my car has presented some strange faults recently , running rich on the Pass bank , lean on the drivers side for example, anyhow , a new loom is now being fitted , and im also swapping the MAF, anyone know why my original MAF has 4 pins in it , but the loom 5 slots, and my replacement MAF 5 pins in it , corresponding with 5 slots in the loom. both MAfs share the same part number

Just to confirm:

 

On the dyno (Leics) it didn't run lean on the driver's side. It had become leaner since the previous remap by about 0.5 AFR which would not have been sufficient enough to cause the detonation that occurred. It obviously wasn't possible to check the passenger side due to having to abort the session. But, if there was a side that was lean enough to cause your issues, I would have assumed it was the passenger side.

 

To answer your question: Earlier MAFs had 5 pins, later revisions had 4 pins. Pin A (orange wire in the loom) is redundant. Both types of MAFs are interchangeable.

To answer your question: Earlier MAFs had 5 pins, later revisions had 4 pins. Pin A (orange wire in the loom) is redundant. Both types of MAFs are interchangeable.

 

I have asked that a couple of times recently and nobody seemed to know, I had the four pin one fit on my 1994 and then I bought another which was 5 pin, have fit both and as you state there is no difference :thumbup1:.