Recently I've noticed a low rpm hesitation in my '91. Idle is nice and smooth and the mid to upper rpm range seems to be smooth, but at around 1500-2500 rpms or so the car kind of hicups and stumbles. Is this a plugs and wires issue? I got the car last July and have not changed them out yet and who knows when they were last done... Any thing else I should be looking for as the cause?