r1997audi

The passenger side exhaust header goes into a tri-flange which has a tap for a sensor (O2 I'm assuming) and another tap that looks like a tube should be attached but nothing was there just a threaded hole and a fitting nut letting exhaust gasses into the engine compartment. The drivers side flange has a tube that goes to the EGR. I have a PO401 code (exhaust gas flow insufficient) w/ check engine light on so I thought the missing tube was supposed to go into the EGR but I can not see any place on the EGR where another exhaust tube connects. Can anyone tell me were this passenger side exhaust gas tube is supposed to go and is it responsible in any way for the PO401 code? Thanks!