Although over 20 years ago, I can't remember my 33 Permanent 4 being gutless below 3000 rpm. Actually quite the opposite, quite grunty!!
It was pretty stock, just a K&N filter element and Autodelta straight through exhaust.
Hopefully with your new panels and the dinitrol it should last.
Mine within 5 years old back in the 90's was not good, the doors were in a very poor state.