Exhaust upgrade????

Hi guys.
When I purchased my Chinese go kart they threw in an upgraded exhaust.
Straight out of the box I thought jeez the header is so much smaller than the exhaust port. I thought the factory one must be really restrictive.
As you can see in the photos the exhaust port is 26mm/ 1 inch, the "upgraded" header has a 19mm, 3/4inch hole then goes even smaller to the header pipe which is 14mm just over 1/2 inch.
Is everyone else running a similar upgraded exhaust?
Is your header pipe also that small?
So after racing my friend on his we have decided to ramp it up a bit and do the air filter upgrade kit and I'm also going to build a better header with 3/4 pipe so it'll breathe so much better.



That's is a weenie pipe and muffler it was mostly used in kart racing as a alternative to the stock muffler. Not much to gain from that little fellow.