Not an expert, but the purpose of the two step was so you could floor it, then release the button on the top light. If the rpm isn't up enough it might bog since the carb is wide open, no pump shot is left. Normally we tried to get 3000-3500 stepping, with just brakes it would creep, that was the point the TB was needed. Of course depending how loose the converter is it might be a higher rpm, then could be more slippage on the top side. I had a 8 inch 3800 conv. but it would push out of the lights at 3000 so tried using all four brakes on the line lock, then going to the TB. Ended up taking all the buttons,boxes out and staging at 1900-2100 , cut good lights and ran the same times.