69 911E engine stalling

I recently acquired a 69 911E with MFI. The car hadn't been run for several years. I took many precautionary steps in reviving the engine, which has 54k original miles. Fuel had been left in the tank during it's layoff. I had the tank cleaned, changed all rubber fuel hoses, installed new fuel pump etc. The engine runs great for a while but will suddenly sputter and die. I've driven around the block a few times with success but am afraid to take it too far from my house as it won't give any warning before stalling. The motor has good power and doesn't spit or backfire on decel.
Is anyone aware of what might cause this? The motor seems to be extremely simple until you get into the MFI unit, and being a novice mechanic, I don't want to tinker with that too much. I know there are a few selenoids and thermostats that adjust mixture during warmup, but I can't understand why it would just shut dowm. I was told the engine ran great before it was parked. Any ideas? Thanks

Before you get into the complexities of the fuel injection, replace all of your filters and use a fuel injector cleaner. Check all of the electrical (distributer, coil, points, fuse block)to make sure you don't have an intermittent short. If a car has been sitting that long, you might have some connections that have oxidized a bit. Also, make sure you don't have a loose ground strap or battery.

Keep me up to date on your progress and try to isolate by elimination of areas of concern. The MFI in these cars is pretty solid, so I would probably look at that last. When the car dies, check for a spark and gas coming out of the fuel pump. If one is missing, you have a good starting point.