It's really a flame arrestor, doesn't do much filtering. As an experiment I pulled off my flame arrestor on my 496HO to see if there was any sort of gain, the result was nothing. Don't waste your money IMHO.
Speed gains are expensive and usually start with exhaust, cam, headwork, and computer reprogramming. You can screw around with some prop work, but in my experience with a low power boat (28'/496HO) it too was a waste of time and money. I just dealt with what I had and eventually bought a different boat LOL!!