I also run the 2-1/8" X 3" B/E Body Super Comps on my 528" Hemi in my 70' Challenger. I figured it was the choking point on my engine but it still made great power for a street engine. On spray they may be my limiting factor but I do plan on going to some custom bigger dia step headers eventually. I added themocouples & O2 bungs to mine for tuning while on dyno & in the car.