Really no difference, and I would argue that for a retrofit the old FOX computer is better, simpler=better. It's not powering space exploration, just an engine To compare processor speeds like it makes a difference is silly IMHO.

DC wrote:

I have a 95 unit in my car and have noticed an improvement in the transition stuff when it matters most. Like throttle response when double clutching and other quick on throttle, off throttle manuvers (really crooked roads). I guess processor speed only matters when you use it. The earlier units are slower, but unless you really push the thing, most will not notice. I sure see it on the track.

It's possible that is simply the difference in strategies, or perhaps tuning if you're doing any? But really no way to tell for sure, good information though.
 

You can plug a MAF pigtail into a SD EFI harness, and the unit will work perfectly with an ECCIV MAF pcm(like an A9P or A9L) The 94-95 Harnesses and pcm's use a different plug with more pins and are not backwards compatible with the older harnesses.
Stick with the ECCIV and you can keep the SD harness. MAF pigtails are relatively easy to add.

Tubo

I do understand that the practical differences of a faster processor may be subtle, but it seems the subtleties are what prevent stammering or hesitation with heavy throttle. Seems that might be what produces a power train that feels like it anticipates what you want from it. The 94-95 processor is said to be 3x faster according to Hakan's first article above. All of the downsides of Ford programming go away with a tuner involved. Which leaves a different connector to one sensor that's wired differently as the only drawback. Provided I can sort that out, the faster processor attracts me.  Think about how different your desktop PC is between old and new in four or five years. Processor speeds can make one seem like a dinosaur compared to the older. The single issue I anticipate is the connector to the MAS. 

Please don't imagine I'm disregarding the advice above.  Simplicity is of value, but the simple thing would be to leave the car carbureted. I'm coming from zero personal EFI experience compared to all of your vast experience. For me, it's batting these things back and fourth that produces understanding. Just trying to politely soak it all in. I've got five months to digest it all. :-)

Tubo wrote:

You can plug a MAF pigtail into a SD EFI harness, and the unit will work perfectly with an ECCIV MAF pcm(like an A9P or A9L) The 94-95 Harnesses and pcm's use a different plug with more pins and are not backwards compatible with the older harnesses.
Stick with the ECCIV and you can keep the SD harness. MAF pigtails are relatively easy to add.

Tubo

Are you sure about the different connector, Corky?  The one we were messing with was for an Automatic and it was a 60 pin just like the 93-back.  I've never thought of using the 94-95 5-spd PCM.  It should be a 60 pin EEC IV just like the earlier ones. 
There were a number of pin-out differences as I recall with the Automatic unit but maybe not so with the 5-spd.

DC...what year is the car you are racing?

BB

Yes we did use the 95 engine harness with the 95 module. Less than an hour to change on my car. I try to route al wiring to be worked on and also out of sight as much as possible.

1996 EEC-V processors (OBD-II) had 104 pin connectors.

http://www.mre-books.com/sa82/sa82_7.html

I agree with Jeremy on not using the 94/95 unit unless you have too. I have never used one on a 94 0r 95 engine. Only time I used one was to get rid of the stumble on quick transitions per the Ford engineer. It worked great for that. Very few folks would ever notice the stumble with the earlier version unless you regularly run on certain road courses. My race car is a 95 GT but because of rules I run a 600 CFM double pumper on it. It has aluminum heads and not a single part in the motor came on a 95. If I had a 95 unit on the shelf and a need I would not hesitate to run it on a well built motor. I don't know about the stock 95GT pinging, since I never did anything with that combo. When I had the 95 controller on my 65 it was set up with the whole 95 induction on top of an aluminum headed all forged motor with forced induction. I sold that set up to someone that wanted it pretty bad, so I now have a 331 stroked GT40 headed set up with a single four barrel in the 65.