Be aware that sometimes trash in the fuel tank can get sucked up against the fuel pick-up screen and restrict flow. Hard to prove that without draining the tank though.
With the filter out and an empty bowl, how fast does the upper fuel filter bowl fill up?
You don't want to see any air bubbles as it fills up.
Have you installed the upgraded fuel pressure regulator spring? If not, you should.
Ultimately, you need to know fuel pressure. Fuel pressure above 45 psig protects expensive injectors.
To rule out other things, you need a scan tool that reads codes and retrieves PCM data (PIDs).
ForScan Lite on a smartphone is a very quality tool for a low investment cost. Other scan tools do not retrieve codes as well as ForScan.
I can help more once you scan for codes and have a tool to pull cranking engine data.
With the filter out and an empty bowl, how fast does the upper fuel filter bowl fill up?
You don't want to see any air bubbles as it fills up.
Have you installed the upgraded fuel pressure regulator spring? If not, you should.
Ultimately, you need to know fuel pressure. Fuel pressure above 45 psig protects expensive injectors.
To rule out other things, you need a scan tool that reads codes and retrieves PCM data (PIDs).
ForScan Lite on a smartphone is a very quality tool for a low investment cost. Other scan tools do not retrieve codes as well as ForScan.
I can help more once you scan for codes and have a tool to pull cranking engine data.