I have a 89 na gxl with the stock exhaust manifold and straight pipes in place of 1st and 2nd cats (only have one left). I had the car up on a lift fixing a crack in the welding and spotted this suspicious looking tube leading to nowhere. (attached pictures) What Is IT???

I have heard before that the ports are actuated by the exhaust in some 2nd gen's but not sure about mine. I have noticed a lack of power on the highway in fifth and I'm not sure if this is related to the ports or this tube for that matter.

I did try to move the actuators and both moved fine.

 

That hose went to the Catalytic via a split air tube.(steel pipe that ran from cat to engine).
It is all I know,I am an s4 guy,so I can't help you if it is s5..sorry.
Someone will help ya though.

 

Yes, the split air pipe from the main cat would connect there. If it's been straight piped, the hose doesn't need to connect to anything.

S4s use exhaust backpressure to move the aux. port actuators. S5s use the air pump. If your air pump is missing, you're down ~40hp from stock. S5s have both the aux. port actuators and VDI actuator running off pump pressure.

 

OK so that makes sense. My air pump is still in place, so my ports must be working. For future reference, what would you use instead of the air pump for the pressure to actuate the ports if you removed the pump?

 

So I'm guessing putting a low restrictive exhaust on my 86 GXL would actually take power away?

 

You just don't remove the air pump on S5 NAs. A handful of people have used electric air pumps or servos to move the actuators, but that's honestly a lot of work for nothing.

Potentially, when my car had the original NA engine, an open exhaust did not allow the actuators to function properly. I ended up doing this: https://www.rx7club.com/2nd-generati...itches-907824/