I need closed loop operation!!!
mines in an 82 Z28 and closed loop hits no problem I just cancelled out the tests and error codes for the sensors I wasn't using and that was all it took sensors deleted include rear O2 sensors (bank 1 sensor 2, bank 2 sensor 2) fuel tank pressure sensor AIR there may be others I don't have my notes handy but it was very intuitive in LS1-Edit as it lists both the code # and the sensor function being tested so either buy HPTuners or LS1-Edit or EFILive or else find a shop to do the editing for you.
However, when I had problems earlier this year with P0200 error code knocking it into Open Loop or Closed Loop/Fault I felt a lot of power loss, though. It knocks down to the Low Octane spark map which is super low advance, zeroes out the LTFT learned values, and who knows what else...the gas pedal felt really lame.
The best performance benchmark I have is on the road courses with nice long straights...it runs pretty much evenly with the four stock Z06 Vettes in my run group. Some of them I can pass, some I can just keep up with. They have better heads and exhaust manifolds, I have more cam and bigger exhaust.

