What will happen if I knock or cut the center plug out of the stock pipes. I know it will get louder but will it sound alright. will it be running to lean or rich

 

I don't know if this answer will help much or not, but here goes:
I used to own/ride a Suzuki Savage 650, and one of the very well documented popular mods was to bolt on a Sporty stock muffler to it and rejet accordingly. Those who knocked a hole through their stock Suzuki mufflers complained of the following results.... LOUDER, SOUNDED CRAPPIER, NEGLIGABLE PERFORMANCE GAINS. When I first got my Sporty, I liked the look of the stockers, but I wanted a beefier sound and more flow... a lot of knowledgable types said don't bother- it may be louder, but it'll sound crappier and not have much of a performance gain.
I would say, try your favorite pair of slip-ons. Just to warn you, I have V&H StraightShots, and they are LOUD. If I had known they were this loud, I would've done a little more checking around.
Hope this was some sort of help.