2000 chevy silverado 1500

Hi everyone!
Long time SD follower, first time posting here.
I recently checked out a 2000 Chevy Silverado 1500 with a 5.3 v8.
As a European guy, not my regular cup of tea.
Between my first check and me writing this, the engine has been completely rebuild. It should be noted that the symptoms have not changed.
The symptoms of the car: misfires
According to the misfire counter on the scantool, it should be cylinders 4 and 6.
I’m going to see the car again this tuesday. And I want to check fuel and spark again. I did this last time, but because of being in a hurry I didnt do a good job of it. Is there anything other I could have missed the last time?
Are there cars notorious for anything? I’ve seen intake gaskets and my friend who rebuild the engine heard that they can have wear on the camshafts. But these two problems have already been tackeld by the rebuild. Hope you guys can help me out or help me on my way. Its very much apreciated!

Thanks in advance

Dennis

To be clear, when you say rebuilt, you mean that the short block came apart? Gotta ask - too many people tell me 'I just had my engine rebuilt' when they had a valve cover gasket replaced. :silly:

Is there a perceptible misfire? If not, then it's probably time for a crankshaft relearn procedure. It's an available function on most scan tools. Even if this isn't the problem, it's a very good idea to do it anyway after a rebuild.

If there is a perceptible misfire, under what conditions does it miss? Does a power balance test agree with the scanner about misfires on #4 and #6?

As far as common misfire causes, the intake gaskets are definitely a common one. But, like you said, that should have been taken care of. Restricted injectors would be the next most likely cause, IMO. If you have a capable scanner, you'll probably find the built-in injector balance function. All you gotta do is hook up a fuel pressure gauge and hit the buttons!

what codes did it detect, does the truck have a camshaft or crankshaft position sensor? also try swapping the 2 missing coil /wire /boot packs to 2 different cylinders and see if things change.

Sorry for not responding earlier. I took a look at the car last tuesday.
Long story short, it ended up being thr fuel pressure regulator. The vacuum connection on the intake was located directly above the start of the intake tube for cyl. This also had a soaking wet plug.
Thanks for pitching ideas!