my 98 S70 n.a. w/automatic has just started to cut out at between 2000rpm and 2400rpm. The car kind of bucks once or twice in this range. I can't seem to make it do it, it just happens. It doesn't seem to happen if I am heavily accelerating.

I replaced the plugs, cap, wires, rotor just 20K ago and they look fine from an outward inspection.

The car has no issues at all when running at 70mph or anything above 2400 rpm (or lower than 2000rpm either for that matter).

Any suggestions where to start looking? It threw a code(check engine light) today, I haven't checked it yet, but I am assuming it is probably a cylinder misfire...not real helpful if it is.