Lower gears and still slugish.

I don't like it when transmissions shift themselves. I dispensed with the kickdown linkage crap and installed reverse pattern manual valve bodies in everything I owned years ago. Never regretted it. You may have more than one issue, but that stock converter needs to go. Skip the 11 inch and go straight to a 9.5 or 10. Call the converter company of your choice for recommendations. Buy, install and hold on!!