1988 Slight backfire under acceleration

As I mentioned in a previous post, just purchased a 1988 Allante. Car is in great shape, starts easy, runs great...with one exception...there is a slight backfire (pop) under acceleration. Sounds like just one cylinder missing sometimes. I do not know the history on this car. Is this a common problem and is there something I should look at first?

Thanks for your help!
Bill