Washer/Baffle in exhaust??

[stuntinFizzer]

So yesterday I welded on my shortened YZF muffler, it sounds alot better than basically straight piped! But it feels like i lost a little mid range power, I noticed there was like a big ole washer welded in my exhaust, maybe by the P.O to retain back pressure while running straight piped?? Didn't know if it was an OEM thing. I plan on just cutting it out, but that means i gotta re-weld my pipe back on

[yamaha_george]

The hole in the power is the shortening of the tuned length of the whole pipe.
If you look on the stock tail pipe there is no washer but a pair of tubes welded at an angle as a baffle to stop the "crack" of the exhaust explosion