Quick update.
As suspected, corrosion had set in on the alloy upright where the arm sits and is held by the pinch bolt. This caused some small play which caused the hole to become oval shaped on the top side.
The upright was taken off and a machined piece of metal was inserted which has allowed the correct fitment and torque settings...so now I have two modified uprights
So far it feels great. Actually the car hasn't felt this tight since I bought it. They also picked up a noisy nearside CV joint which was replaced as well.
I will run it for a few weeks to monitor it but so far the "issue" with the rear suspension seems to be gone. In theory the uprights should not cause any further issues. The litmus test will be when i hopefully get lowered suspension fitted next year. If I get any problems I will look at brand new uprights or adapt other models with iron ones to fit.
Thanks for help guys.
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2002 S8 - Irish Green Pearl. Cat N (saved by the D2 Doctor
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1988 E30 Coupe - Royalblau Metallic
2003 S4 Avant - Light Silver Mettalic
2016 S5 Coupe Black Edition - Ibis White