I think you have fallen for urban myths on drilling the exhaust. 2 strokes perform best with a certain amount of back pressure on the exhaust; no manufacturer makes a motor with too little exhaust outlet.
A very few drag racing V-6's have benefitted from some exhaust relief when the normal exhaust outlet was far deeper in the water when the boat was launching than the manufacturer intended (small boat, BIG motor). Just because it helped one motor doesn't mean a modification should be done to all motors.
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