Hi Dave! The way I understand it is that the reaction tubes are heavier gage metal than their predecessors and accumulate the heat from the heads/exhaust to help burn off unburnt fuel vapors, but I don't know the chemistry involved. We know the 75-76 engines run hotter because of this exhaust system and it was the intended design for emissions purposes. Here is one page from teh 1975 S&T manual, it identifies the exhaust system parts, but doent explain their function. What say you?
