It's unlikely it will do anything for you. Lead is non-ferrous and as such has little or no effect on magnetic fields or RFI. It's also hazardous to leave it out and not seal it in some way. There are many good metals that could be used around cables and components. One is marketed and sold by Percy audio. It's a copper alloy sheet which I've tried and it does work. I used it to shield the tubes in my phono stage from other interference.
