Holleya#39;s installation manual lists procedures for tuning the midrange and high- end power, which basically involves tuning for best mixture at 3, 000 rpm unloaded in ... The Pro-Jection system was a vast improvement over the carburetor on the Challenger. ... The single-plane Edelbrock manifold on the Challenger uses runners that are perfectly in line with each other. ... I used a 39- psi pressure-referenced regulator from an L-Jetronic injection system, and I robbed the Bosch fuel pumpanbsp;...