great thread

regarding back pressure - depending on the size of the exhaust system (and number of boxes, bends, length etc), then having the outlet of the external wastegaste returning to the exhaust system will in all likelihood have an increased back pressure over one that vents separately. it is simple physics as more mass flow will be going through the main exhaust system (although there are many factors involved and you would need back to back testing on different 'screamer pipes' to prove it)