I did my Masters by Research on this subject. "Investigation of pulse tuning the exhaust manifold on a turbocharged engine and its effects on engine output." There are very interesting results into pulse tuning with regards to pipe length and diameter including the effects from camshaft timing and how EGT effect the speed of pressure waves. I had pressure sensors in the exhaust system measuring primary pulse waves and how they reflect/refract and attenuate as the engine is running. I measured in cylinder pressures and have many results. I would be happy to show all my research paper once submitted in November.