1990 Ford Mustang 1990 Mustang Itermittent Stalling

I have a modified 1990 Mustang GT, (cold air, performance pcm, 24lb injectors) The problem I am having is an intermittent stalling issue. In gear, the engine sputters, stumbles, then dies. When I go to restart the engine, I usually have an electrical "crackling" sound coming from under my intake manifold and my tachometer needle bounces up and down. I have so far replaced the entire distributor, including the TFI module and plug wires. I put a pressure guage on the fuel line and have 32psi at start up and during operation, but a loss in pressure (10-12 psi over the course of about 15-20 seconds) when the key is out of the ingition. I have also replaced the fuel pump relay and fuel pump. I've also checked my grounds and my igntion switch. Today, when it died, I had a large amount of white smoke come out of the exhaust before it turned over and it was struggling to continue running for a few seconds. Then it settled down and ran well enough to get me the mile or so back to the house. Any ideas?