if you like the power of a straight pipe like that, you should consider getting a tuned expansion chamber. it will give you the power, some of the noise, and it will be ok on the engine. you MIGHT have to richen the carb up a bit, but that's not hard to do. but yes, running it with a blown exhaust gasket will make the motor run a bit leaner than it should. i have seen people running a straight pipe with no muffler at all (but with a good exhaust gasket) and the motors have good power.
but really, a 2 stroke will make more power with a non leaking, tuned expansion chamber rather than a leaking stock exhaust. backpressure is what helps the cylinder stay filled to capacity to make maximum power. an expansion chamber raises the amount of air/fuel that is packed into the cylinder for even more power. it will also add a supercharged effect when you get it into the power band at a certain rpm. (depending on how the pipe is tuned). i have read that you can expect 1/2 horsepower gains by putting on an expansion chamber exhaust.