have a stock everything 454mpi bravo 1 with thru hull and silent exh there is resonators in the exhaust tube i heard right? if i took them out it would sound louder and better right?

They're there to prevent reversion- the backwards exhaust pulse caused by cam overlap- from pulling exhaust water into your engine, splashing on glowing-hot exhaust valves and causing them to separate from their stems and pierce the tops of your pistons.

But you can take them out if you want

if i buy headers do they come with them too?

Headers will have more rise to them and then more downward angle to your transome.
When I had stock 454 mags, I removed the resonators. Yes it was louder, not sure it sounded better. But, I also lost RPMs and speed. The stock exhaust like more back presure.

Are we talking mufflers in the exhaust tips (Corsa Tips) or resonators in the exhaust piping? Chris, will replacing Corsa muffled tips with open tips create a reversion issue? My exhaust doesn't have resonators because I have Silent Choice (per Merc recommendations), but I did have muffled tips. I wanted a beefier sound, so I gutted out the baffles in the tips. Sounds great, but I don't want to be ingesting water either. I kept the stock rubber flappers in the exterior and the left the internal flapper in the tip. Redundancy can't be a bad thing.

There are little plated between the manifold and the collector that have a flare to them- these help aid in stopping reversion.

Reversion happens because of where water is injected into the exhaust stream. On a stock Merc, it's right at the end of the manifold- inches from the exhaust ports. On something like the Stainless marine with the short Bravo risers, it's fairly close as well. The Gil "dry" pipes I have on my Cig mix water into the exhaust at the last half-inch. And, since they're for a boat with transmissions and come up from the center, they're really long- four feet from the manifold. No reversion there. Mufflers can actuallu make the situation worse- idling with them on allows some water to pool in there- the more water and the closer, the higher the likelihood of reversion issues.

Removing the baffles in the exhaust won't add any to the reversion effect. On stock engines it can hurt you on power- sometimes the engine likes a little backpressure. Over about 350 horse that goes away. Flappers really don't help or hurt- they're ther to keep big splashes out of your pipes- especially when not running.

On stock cast iron Merc manifolds is the water not entered into the exhaust stream past the end of the riser, not the manifold?

Removing the baffles in a Corsa exhaust tip (those butterfly looking plates) will not make your exhaust more prone to reversion as long as you retain the internal stainless flapper (if present) or add or retain an external rubber flapper. They do help block water from a wave being forced back up the pipes at idle or sitting but they won't keep water out on their own.

Yes, they mix at the riser- just at the end of the manifold. Probably not very clear though. Merc exhausts are about the worst for reversion- the riser mixes the water in way too close to have any cam with any overlap.

Agree. Hardly any length to the riser towards the transom and away from the manifold.

I am sorry I pulled mine out...too noisy in harbors....only gained 1 mph..