Tuning Demon Carb on Stock 460ci Pickup Engine

Been driving with the last mentioned configuration for a few weeks now (82/86). Truck runs fine and starts good. Aside from a sticking high idle cam the carb is still good. Issues to mention though is when I floor the truck from a lower speed (tried this at 25mph) she accelerates fine and without any hesitation but the engine starts to rattle the faster you go starting at around 45-50mph. With the last statement, I wasn't watching the exhaust as it was dark in the area I was in.

A little bit later I got to a lit area and floored the pedal at 35mph for a few seconds, a medium black plum of smoke came out and lasted the whole time but faded the longer I had the pedal down to the floor. I know these aren't the greatest tests but I was on an open stretch with no one around and decided to test the new configuration out a bit.

Other than the vacuum gauge as mentioned above, what kind of little/simple things can I test this configuration out that might point out way to start the fine tuning.