I've asked around on a few forums and still no answer. I'm looking to upgrade my ignition for boost. I'm looking for a box to retard the timing based on the amount of boost...the only problem is these boxes use the map sensor to measure the amount of boost for retardation. Mine is a 91, so it doesn't have a map sensor. I've been looking at MSD 6btm, similar summit and mallory boxes to the 6btm. How would the box measure how much boost is in the system? Has anyone hooked up an ignition box for boost and how did you do it?