are you referring to the istersi of the N75-wastegate?? and, anyway, for your info megamind the volumetric efficiency of a 4 valves per cylinder and abundantly more than 95%....I believe even more now that for the design of the inlet and exhaust ducts for the choice of the timing of the distribution you are using the most powerful sw simulaziuone 3d...85% of VE, and a typical value of an engine 2 valves per cylinder...