My friends 2000 z28 has noticed a faint tick coming from the drivers side head. His car only has
31k on it and it
stock besides an slp lid. I figured it might be his oil that was sitting over winter(old 10w-30 conventional). So we ran some seafoam through it and put in some GC 0w-30. The tick is still there and accelerates with the rpms. Also oil pressure has dropped with the GC and kn oil filter.

It was 40 idle/ 60 cruising. Now its like 35 and shaky/ 60 WOT??? When I changed I gained like 10psi everywhere.
Please give some advice on what to check first. Were thinking either roller rockers or lifters. But I thought lifter ticks went away when the car warmed up.
Thanks.