An engine with a large enough overlap triangle area* (from Vizard: OL area ~ OL Degrees^2) to benefit significantly from tuned exhaust will experience less pressure differential to the chamber with any disturbance to the exhaust return wave (diametric change, more volume, restriction).

Very mild engines may not notice any change.

* For OL area comparison using nominal valve events (IO @ BTDC + XC @ ATDC), 70 degrees is not 40% greater area than 50 degrees (70 / 50), but 70^2 / 50^2, or 96% greater (4,900 / 2,500).