Performance Exhaust Loud and Slow

[skyrider]

Just got a $180 stainless performance exhaust and uni dual filer for my QMB139, and with a new gasket or old gasket, its loud and I have no power. It barely gets to 25. ( I was getting 40 on a flat rd with 200lb. of me.) Took out the carb and there's a big hole in the main jet so I guess its letting enuff air in but I'm ready to paint my old muffler and sell the exhaust since I can't return it. My regular setup was perfect power for me, variator set to get my heavy ass up hills, I just was tired of looking at a rusty old exhaust.

So is there anything else I should do to get more power and quiet before selling? (Please Pm me if you want a new exhaust)