Jolly: Just tried to Google some info on the augmenter and found this, from a Piper Apache manual:

The exhaust system is a cross-over type with exhaust gasses directed into jet augmenter tubes located on the outboard side of each engine. This system provides for exhaust elimination without power loss, and effective engine cooling through the pumping action of the exhaust gasses into the augmenter tubes, which draws cooling air through the engine compartment; no cowl flaps or cooling flanges are needed on the cowling. Higher aircraft speeds are obtainable with this system due to reduced cooling drag and due to extra thrust furnished by the exhaust augmentation.