intermittent miss at idle 1987 420sel

[mb420]

Occaisonally at stoplight car acts like its running on less than all eight.Hard miss. pulling away from light, slight bog, then smooth as silk. I.m leaning toward fuel related, but have only had car a couple of months and don't know how it was serviced other than a/c converted by MB dealer. Car is almost showroom with 138k miles. Shows 2300 rpm at 70mph, is that in ballpark? 1987 420sel

Any and all help greatly appreciated, Art