VSS not working

[A fireman]

Hey all, About 2 years ago I changed the trans in my 94 bird from an A4 to a M5 but turns out it was from a 93. As a fix I replaced the pcm with megasquirt 3 and a pulse generator where the speedo worked perfectly. I am currently putting the megasquirt system in my LT1 formula instead of dealing with a 4th burnt pcm. I have established the new sensor is putting out about 4000 pulses per mile but the computer reads at most 3 mph. Dose any one know what settings need to be changed to what so I can get my speedo working again on the stock computer.