Hey, So today I was cruising on the highway in 6th gear. I recently did a idle tune up (IAC and TPS) and had reset the computer by pulling battery cable. After doing that I was driving it to recalibrate the speedo. I have a dakota digital converter on my t56 to convert to mechanical speedo. So I was adjusting the system and I hit the PPM button and my speed shot up on the speedo. Then I changed it again and the speed went to about 120mph while I was doing 60mph or so. The moment it did this the car surged then immediately died. Pulled to the side. Car started fine however as soon as I drove i got to 100mph (according to speedo) and it sputtered and dies again. Then I try again this time keeping it slower and it would run till I would get to around 80mph (again, not real speed). So I reset the dakota box and set it for auto calibrate then everything was fine! Has been fine since then. How the hell can the dakota digital speedo converter be causing my car to die??? VSS issue and confusing the computer?

Thanks!