performance tips new merc 25hp

I have a brand new mercury 25hp, its a sea pro short leg that I’m using on a high performance boat, I have heard that there is a spacer between the carb and manifold that has a restrictor in it, apparently if you get a round file and open up the spacer to the same size as the carb, its a 30 hp. apparently the only difference between the 25s and 30s is this restrictor? Can anybody confirm this?
Same engine, apparently playing with the ignition and advancing it will give me an increase in power, does any body have a procedure I can follow to do this?
At the moment Im thinking of just make adjustments of 1 turn of a time and seeing where the sweet spot is.
I have a gps and tacho so I was planning to log the info and see what works best
Any other tips for speeding up the engine?

you have had 13 looks at the problem and no answers....that probably make 14 of us wondering why you just dont get the prop for the rig that turns the rated rpms....a 25 hp is what you got and trying to jack up a new engine could result in an expensive conversion to a pile of junk...just my opinion my friend...

Way ahead of you i have a number of props and adjustments to fine tune the drive side of things to which i am very familure with, but i need to acheive maximum engine power to acuratly tune the drive and to be compatative, answering my own question a bit, i pulled off the carb and the spacer behind it had a 16mmx38mm s.lot in it and the carb and m?anifold diameter is 38mm, i have opened up the slot to be 30x38mm now which looks like it will incrase the flow alot, im still wanting to play with timing and possible main jet adjustment?