Top End Miss

I ran that red pump tru a regulator on a 625 Holley vacume secondaries carb at 5.5 lbs..NO issues with my close to 1,000 lbs lighter car.My carb was a 600 but has been worked.He is heavier and running more carb on lesser engine,with more gear.I hate to admit it,,butt he might need more pump.Black pump with a REGULATOR set a 6 lbs running will just tell me I was at the brink with that red pump,and not enough for his car.VERY CURIOUS.Btw my car ran the same with my new black pump at 6 psi as it did with with the red at 5.5. Mark