Wow, this one went WAY out in left field.

Lower octane fuel will NOT cause misfires. It retards timing evenly.
Vacuum leaks are most apparent at idle, not cruising.

This is an ignition problem. Plugs and wires as stated (stay away from Bosch, and stay away from ALL platinum plugs. Copper or Irridium only). Stay away from Bosch or Taylor wires. Both have very bad reputations here. OEM wires or Belden Premiums from NAPA are best bets.

At the same time, follow the coil pack troubleshooting in Techinfo (link at the top of the page, or search the Techinfo for 'coil'). You may also find rust on the coil secondary terminals. This is common on the Series 2 motors. If you do, clean them well with a wire brush and some scotch-brite (in the body/paint section of the parts store), and reassemble with dielectric grease. Also put some of the grease inside both end boots of each wire to keep water and such out, and make your next plug or wire change much easier.

I am experiencing a problem that sounds much like that, with the exception that it seems to worsen when rounding a sweeping curve. I almost wonder if it could be trans related.

I have already replaced Plugs, Wires, Coils, and TPS all with OEM parts. However the problem still exists.

RMP, your problem may not even be closely related. Feel free to start your own topic and be as specific as possible in your symptom description.