Compared to the as-cast TFS R heads, the CNC version improved the peak airflow by 36 cfm on the intake and a like amount on the exhaust. More importantly, the flow numbers improved throughout most of the lift range, with the exception of 0.200 valve lift on the intake side. While more peak lift flow is good, more average flow throughout the lift values is of greater importance. Using the power versus airflow formula (Horsepower = Peak Airflow x 0.257 x Number of Cylinders), the CNC porting improved the power potential of the R heads by nearly 75 hp over the as-cast heads.