There is a bit of a learning curve when going from a low pressure, carbureted, mechanical fuel system to a high pressure, EFI, computer controlled system.
First, don't think of EFI as a carb replacement, you really are changing the entire fuel system. The fuel pumps, regulators, filters, pump locations, fuel lines, will be different, and usually EFI will also use a return fuel line from the regulator.
The high pressure EFI fuel pumps are not good at creating suction. An In-Tank pump is usually the best, quietest, and adds lift to the pump. Most In-tank pumps come with an inlet sock type filter. If using an external pump, it should have a low restriction 100 micron or less inlet filter. Pump outlet filters are usually 10 micron, and I think Holley says max of 30 micron? The pump outlet side is high pressure, usually 3 or 4 Bar (43.5 psi or 58 psi) on normally asperated engines, and higher on boosted engines. The fuel lines, connectors, clamps, and fittings need to work with the higher pressure (and with todays alcohol enhanced fuels.) Most (if not all) aftermarket EFI conversions are setup to use -AN fittings too.
Using your old corroded fuel lines with EFI can be a problem if it is past the fine filter. Any crud that gets past the fine filter can clog up an injector.
Carbs can run OK with some sediment that gets into the fuel bowl.
If your used of seeing a constant fuel pressure going to your carb, the EFI fuel pressure will vary depending on manifold vacuum/pressure.
Anyhow, I think the fuel system is where many people new to EFI make mistakes to where they complain they have a "bad injector" when it is likely has trash in it from the old fuel system. I think the electrical wiring most people handle fairly well, but get lost with the EFI terminology used for programming/tuning the ECU software.
