I think the coils rdoyle is referring to are sold by apb enterprises, they have a pinside shop which markets specially made lotr coils. I had the PBL coils in my game when I got it and I felt they were just too powerful and gave these a try. I think the game plays much better with them installed. Just make sure you get the ones specific to your machine (Standard edition vs limited edition).

If you are referring to people installing the apb enterprise coils, just for the flippers. Deal is that a lot of people had trouble with original coils weakening over length of the game. So a lot of people installed the PBL coils which do not weaken but some find too powerful for the plastics, ball flying off ramp, etc. the apb ones are kind of in the middle of the 2. Don't weaken but not too powerful.

Regarding the slingshots, I would rule out mechanical problems first as looks like they may be binding. Would check plungers, links and coil sleeves. I have a buzz on my lotr flippers sometimes and would be curious also if there’s a problem it may or may not signify

Re: flipper coils losing power, that’s why a lot of people switch them out. Pinball life sells high powered ones. Those came with mine but I found them to be too powerful so replaced them with the mid powered ones that apb enterprises sells through their pinside shop. I found those to work well.