EFISupply handles many popular sizes of 4150 and 4500 series "4 barrel" type throttle bodies. While carburetors are better undersized than oversized, the same cannot be said for EFI throttle bodies. Using an undersized throttle body will unnecessarily restrict airflow. Care should be taken to going too large however as using too large a throttle body will result in a lack of throttle "resolution" or sensitivity and may negatively impact drivability. We have found that the 1200 cfm 4150 flange units are well suited for naturally aspirated efi applications from 400-600hp and the 1550 units to work well from 500-800hp. Applications making more naturally aspirated power are likely equipped with a 4500 series throttle flange and should employ a 2000 cfm unit. If you're running a wide open application which requires little throttle sensitivity, you may opt to go with the big 2600cfm unit. For additional information, please contact our technical staff at tech@efisupply.com.