It's basically an updated version of a carter thermoquad. I'm not an expert by any means, I'm just throwing out ideas. How far did you set the secondary airdoor spring tension? I know on my rebuild manual for my thermoquad it says to give it about 1 1/4 turn to set the initial tension of the spring. I'm curious to see how far you have it now and are still experiencing a bog. Also you could look at adjusting your metering rod step up spring. I had issues with my tq and I "richened" up the mixture by adjusting my metering rod tree. You could get a demon calibration kit and run a larger jet I think, but I'm not totally sure. Sorry if this wasted your time, just throwing out ideas. Love the car by the way!