EFI for my 340 Duster

I’m fighting with a Holley Sniper on my 408 Duster right now. Ran great for 6 weeks, now if it starts barely idles. They are telling me rfi issues. Not totally sold in that. The connections come out of the Sniper (and I bet the Fitech too) right by the distributor and wire bundle by the firewall. Doing it again I would put shielding in the wires during the install. Then again, know a guy that put one one his 408 Dart, no issues. So wtf?