My DTI TT-20K just arrived in the mail so I'd like to mod the muffler on the MS660. As I understand it you basically enlarge the hole (or create another one) so the total area is about 75-80% the exhaust port area. Then re-tune (2,500 rpm idle and 13,500 rpm WOT as per the manual). Does that sound right? Can I get rid of this little cage thingy inside the stock muffler?