Do catalytic converters really run your engine that much hotter reducing engine life? Picked up my new 19 BO last week with stage 2 but stock headers and some are saying I must get rid of the headers before I stuff up the longevity of the engine. M8 cats I believe are now modified to run cooler, plus a dyno can tune the engine to almost ignore the cats. I'm a novice to all this, can anyone confirm any of this?  

They run a lot hotter with a cat than without. Most late model HD have a function that allows the rear cyl to cut out at a certain temp when idling at lights etc. Cut the cat out and retune

Yeah they run cooler

Some modern cats flow really well and that was one of the big reasons they were ditched, not sure Harley is up to speed there although I've seen dyno sheets of late with good numbers with stock headers.

The issue is on Cold start the cats do nothing until they are up to heat.

If you look at the cold start part of the map on the new bikes it's leaner than what I would call acceptable, this is to get the cat up to temp and in it's operating zone.

The actual HP difference isn't as big as you think, I'll find a chart when I get in.

Not quiet on topic but still a good gauge regarding heat

Good table.   My thoughts are:  Is the reduction in temps actually of any significance?  ie are the original baseline temps within the operating range of the bike and oils in the bike?

My oil temps on the M8 never changed after going to an open header. The HEADER certainly runs hotter with the cat in place, not noticeable on Tourers though, your foot is nowhere near the cat. The cat kills a load of dB though, factor that in if going catless on a M8, it easily doubles the noise...

Agreed. Just some bloke on a FB site said I should of changed my headers before I put the cam in, as the engine runs way hotter both with the cam and the cat still installed and that it reduces the life of the engine. With my new cam and my slip ons installed the bike is super loud. I would love the V&H big radius but as you say it would double the noise without the cat. It would be obnoxiously loud and it’s something I’m not prepared to have.

I run a decated std headers with V&H mufflers, was too loud so switched to their quiet baffles. Big difference

Apologies if I'm wrong....The cats on a 19 breakout...aren't they in the mufflers...if so I would keep the headers and just fit slipons

Shit hey. I didnt know that. I've got aftermarket slip ons with my stock headers and all this time I thought the cam is the reason why its so loud. 

I bought a '17 street glide and the cat was in the header,because of the cat located in the header, the primary side exhaust was 1 & 3/4"....the high side pipe was 2 1/4"- 2 1/2" ? "..so not wanting to shell out for a new set of headers i bought slipons to fit...in 2018 the cats on the tourers were fitted into the mufflers....that pissed me no end...

The cats in your 19 Breakout ARE in your stock mufflers, not the header. So, if you run AM slip ons, you are catless.