Check out these worthwhile addition’s to improve the S4 chassis, when fitted the front becomes more ‘pointy’ and the overall balance of the car is more tactile & precise, I’m convinced the S4 designer intended the front strut to be a standard fitment, the mount point is on all S4 chassis, - check out the John Tipler ‘7’ book ‘Racers for the road’ page 61 which shows the prototype S4 chassis which has the strut fitted. It’s also fitted to the famous S4 based ‘7X’ racer of Tim Goss also featured therein. Cost probably prevented it’s use on the production car, without it the chassis was deemed adequate for road use.
The rear strut was also omitted from the production car, though the moulded well in the boot floor on all S4’s indicates that this was left out at a late stage in the development of the car. And like the front mentioned above, was a well known 1970’s upgrade.

Yep, upgraditus’ was around in the old days too. Us old git’s empty pockets remember them with love & affection!!

If your car doesn’t have these two struts they are well worth fitting.
In fact - I’d say it’s the best upgrade for any S4.
£500 ought to get you both. Or make em’ yourself like I did!