I have a Comp Cams Retrofit Roller in my 69 Mustang 351W, number 35-452-8. At the moment it runs poorly. Only 6 inches vacuum at idle which will not operate the power brakes. I have had several good running engines in my day and this is not one of my favorites. I am contemplating pulling out the cam for a different grind. The one i have is 230 deg duration at 050 lift and .544 valve lift and 110 deg lobe seperation. I just talked to the tech help ;ine today and they confirmed that the cam is performing as designed. For more vacuum they suggested 114 deg lobe seperation. They can custom grind one for $250. I am looking around at some other brands but really have not found a whole lot that i would be willing to try. If i was doing it again i might be tempted to use a tried and true standarad hydraulic where there is a wider selection of cams available.