You can adjust the piston position at the top of the clutch pedal. Move it towards the firewall. You might want to check that the hydraulics are working properly first though.
Also make sure not to adjust it too high, because then, when you push the pedal to the floor it can over extend the clutch fork and the master cylinder.
There are different R180s too... I only have direct experience with the GC8 Type R/RA diffs that have clutch packs... the circlips are internal with these.
Some of the later STis have a viscous rear R180...pretty sure the axles are the same though.
It should be pretty obvious by the depth of the groove. A deep groove on the axle stub will probably mean a circlip is supposed to be present. A shallow groove probably
means the circlip is inside the diff. You can also put your finger in the diff and see if you can feel the circlip... should be easy enough.
There are quite a few different rear diffs on these. Some have circlips on the axle stub, and some have them internal to the diff.
Some have equal length axle stubs, and some have different lengths. Something only one side has a circlip on the axle.
Fuel enrichment when cold causing issues maybe? Or maybe the temp sensor is bad, so fuel enrichment is not happening.
There will be a bunch of things different in the tune when it's cold.
Expect to pay around 10k for a decent rebuild. Maybe 8k if you take short cuts... 12k if you do everything properly.
Removing the engine and taking off the heads will save a bit of money... but the costs just add up and up and up.
There are diagrams around... you just need to search for them.
It's very likely that Joker is correct though. Just a spare plug with some power going to it, so useful for some previous owners to hook into for whatever.
Thanks.
How big were the fluctuations, if you remember? I am seeing +/- 0.25 psi at idle.
Were they a problem for the tuner, or you just judged them as warranting the dampers before it got to the tuner?
Front diff has gone bad, but only when warm? Sounds weird to me. Could just be some worn bearings somewhere. You should get it properly diagnosed before trying to find a new box.
A replacement box though should only be $300 to $500. Labour will be easily $1000 these days. You'll probably want to change the clutch and replace or machine the flywheel. Several hundred more dollars there.
But if it's just a worn CV or wheel bearing, it'll be much cheaper!