E.F.I. systems have sensors constantly testing the fuel ratio mixture so it adjusts to feed the proper fuel mixture in.
Many run their ported and polished cylinder heads with the stock fuel injection system and are quite happy.
This is definitely the way to get the best fuel economy.
There are benefits to be had with a high-performance fuel injection system.
I've put together a few books found below, to help you.
A practical guide to modifying and tuning modern electronic fuel injection (EFI) systems
How to install a complete aftermarket EFI system.
How to become an expert in modifying fuel injection systems for increased results.