It sounds like without the baffle you were getting reversion. Reversion is when the shock wave travels down the pipe, then back up and hits the valve when open at certain rpms. If it hits when the valve is open it keeps exhaust form exiting, and keeps the intake gasses from going onto the cylinder.
On real bad cases it can even fart out the carb.
The baffles break up the shock wave and smooths it out so that there is not a reversion back up the pipe.
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