Depends on your intentions for sure. I will use the best flowing valve tested. Thus far it is the +1mm Ferrea for me but I have only tested stock valves, Supetech +.5mm, and Ferrea +1mm. I found low lift increased by going with the bigger valve. I won the Ferreas at Z-Nats banquet last year, Thanks Z1!! Melissa (Drifts) handed them to me and I was stoked!! Thanks Melissa!! So, the Ferreas were free to me but it would not matter as I had intended on testing them and it turns out I will be using them. My goal is over 1000whp so.... I have spent thousands of dollars on tooling and 100s of hours testing port flow design.