'83 Volvo 240 stalls when downshifting

I have an '83 Volvo 240 Turbo that only gets driven a few months out of the year. After returning this year, I had the fuel distributor replaced. It ran very well initially, until it started stalling out when I would go from higher gears to lower gears. It goes like a dream on the highway, but as soon as I get into town, it starts stalling at every light. It starts right back up again without any trouble. If I have enough distance and give it gas while slowing in neutral, I can prevent a stall most of the time, but obviously this is not a solution. Any suggestions?