Hydraulic tappet ?

dawudih

I'm not 100%, but car engines primarily use hydrolic lifters (maintenance free) & sports bikes use solid lifters (higher performance & maintenance). There were a few Toyotas & hondas that used solid valvetrains, I think in the late 80's, but it's primarily used on high performance bikes.
The Nissan probably uses hydraulic lifters on the exhuast; I don't think it has a traditional cam on the intake side. I've seen an Infiniti's head & it has a complicated lever system to control the intake valves lift & duration while the throttle butterfly is almost always wot to reduce pumping losses.