I was planning on selling my PS One R50 shortly but can't afford to upgrade to an S at this stage so need to decide on more mods!

Ignore my (lack of) logic!
I've been thinking upgrading my manifold, will an R53 manifold fit perfectly? Will this add a lot of power? It's decat. If so, anyone got any idea how much? I'm a bit of a newbie when it comes to stuff like this so any advice would be good!
Another query I have about a decat manifold, will it make a massive difference in sound? I understand it might pop and bang a little bit, but will it be a lot louder?
Thanks in advance!