Just had a thought for everyone: I had JUST put on a new Powermaster 95 amp alternator. In fact, was taking it out for a longer test drive the first time it stalled on me. Any chance that 95 amps isn’t enough, and that’s causing the stumble/stall?
Why on EARTH did you put such a high amperage alternator on it? Do you have a window unit A/C in the back window? You're just asking to burn that car to the ground now.