Or the cylinder pressure, or the elevation you are operating at. I see Wiki says the highest point in Ga is 4784 ft,while the lowest is sealevel. That's gonna make a big difference .
As will a 2.20 rear gear, a bad exhaust, a bad cylinder, or a bad TC. etc.
You need somebody competent to establish a baseline.
BTW
The SS 2bbl his tiny tiny venturies to help in making fuel mileage. With no other changes, I doubt you could measure a performance improvement over a good operating single bbl. In fact, Ima thinking my engine was stronger with the 1bbl
