My vaccum stays 1-3 kpa from baro untill over about 4200 then it drops 3-6 kpa.

I guess this is normal for the stock 5.3 truck cam right?
Just making sure that theres no restriction in the intake or anything.


I heard a long time ago that droping your timing at peak torque was good.
The stock table looks like it shows a little peak at around 4000(peak torque).
The problem I see is that the torque is pretty much even throughout the rpm range so at 4000rpm its probably only about 10-15ft.lbs. more than at 3000rpm. So is the 1-3degrees drop in timing necessary?