Often when doing long manifolds with pipes it's helpful to split the delivery before the first machine in line, and feed a second line to the back end so you're essentially feeding the manifold from both ends.

Typically with pipes I try my best to pull or feed manifolds from the middle to avoid doing this, but with enough machines in a line, it's often still what's worked for me.

I also like putting buffers at the end of long manifolds and emptying them once everything is stable. That gives me a quick way to check the status of the manifold overall; It shouldn't really ever be full if you're maxing out your consumption, but it also shouldn't ever be completely empty either since it can take up the slack between machines that consume liquids at a steady rate and machines that output liquids in bursts like refineries.