The problem could consist of quite a number of variables. I can only speak to my personal experience with my 2000 Stang. I had a similar experience and, to make a 'very' long story short, it turned out to be the electric fuel pump. I ended up dropping the tank, replacing the pump & filter. It hasn't caused a problem (with the ignition) since. However, I did have a heads up. I purchased an OBDII diagnostics unit and pulled the code that led me to the problem. I also bought a Haynes repair that has proven to be extremely helpful for years now.
One question: have you tried running diagnostics to see if there are any codes?
The road to enlightenment can be a bumpy one. The road to stupidity.....deadly.
...Bob Sintzel 2010