Comparing the supply to return line I would expect the return to have a higher line resistance based on the following.
I have an 8an pickup line from the tank to the pre pump filter, then once it's at the pump I have 6an line to the small filter and then FiTech unit. This should have very little restrictions. Now for the metal 3/8" existing line that I am using as a return it was an oem copy but larger diameter. Measuring it appears to be 3/8" outside diameter. Then with the various bends, turns, etc I can see how this line would have a different resistance rating than my supply. Due to the resistance difference that's why we were thinking it could be an issue. If the return pressure is low could I do a quick trial with standard fuel hose back to the tank and see if it make any difference or at least eliminates the return as the culprit? I hate to spend $105 on efi hose for the test and if it's not the issue. If it does fix it I would swap out thw line to efi rated right away.
Anyways thanks again
You said your problem is mostley at WOT? Like was allready mentioned, thats when you need the MOST fuel, so return flow is probally not the issue. In your picture, you just have a pickup laying in the tank, with no baffles....I would suspect major fuel slosh and air.......
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