looking at upgrading my exhaust from a 4" wet gil risers to 4.5 dry. I had considered headers but after some research it appears most people dont get much of a performance gain over the manifolds i already have. So whats all the advantages and disadvantages of the wet vs the dry. other than i know the 4.5 dry is going to sound better. Engine is a modified 525SC. 468 cu in. Roller cam with .600 lift. on a regular engine dyno it made 570hp and 600 ft lb.

The only thing you will gain is noise.

I doubt you will see any power. dry is super loud though and even if you love the sound will get annoying through a long idle zone.

Everybody I know who ever went to a dry system is either deaf or switched back to wet. Just not worth it.

Have 2 950hp blower motors with Stainless Marine Completely Dry 5" tails and they arnt loud enough!!!

Two 800HP blower motors with Stellings headers and dry tails, it aint that bad....
Dry Tails can get really loud idling if your running a big compression, long duration cam, big ported heads, etc. But most supercharged marine engines are low compression, modest cams, and really aint that bad at idle. Ever heard a stock 454 suburban engine with open headers, then compared it to a 700HP N/A 454 strip motor with open headers? The suburban 454 sounds tolerable, the 700HP sounds like a monster.

While at certain HP levels, you may not see much gain going from a GIL manifold to a header, but...at some point a good flowing set of headers DOES make a difference. On a 450HP engine, no, but a 900HP engine, it can mean alot.