I have a S5 NA RX7 and I'm thinking of running either water or seafoam through the intake to clean away any carbon in the engine. However, after searching the forums I couldn't find anyone specifying exactly which vacuum line to use on the S5. So which is it?

 

Any vacuum line will work. There should be a good sized one coming off of the brake booster.

 

I'd pick one that is Upstream.
I mean that will actually share airflow to both rotors.
(I haven't done it,But I would pick the biggest one,besides the booster)

 

You mean like the one right on top of the engine for the AWS.

If you use this one, go for a drive and be sure the secondaries and the VDI system gets cleared out, because some of the water/seafoam gets trapped in those areas.

 

Would you happen to have a picture of this one?

 

It is on the drivers side of the dynamic chamber. Big rubber hose jus like the brake booster line.

 

Is it the hose on the lower right?