Great Volvo is stepping up and doing the right thing even at 40k mi.Audi isn't so forthcoming on the S4 V8's, they know which 1200 engine could fail and do nothing hoping the engine holds together until out of warranty then the owner is responsible for the new $25k engine.
The Engines had weak valve springs which would fail causing a valve to drop into the cylinder(was mostly the #8 also toward the back)this caused head damage or total engine failure (sounded like an old smith-corona typewriter)
Audi's first response was to blame the owner then try and replace only the head, ignoring the cylinderwall damage caused by the valve, then the whole short block, crazy but true. Service deptments were explicitly prohibited from opening a bad motor which was shipped back to HQ in Germany. Same went for bad gearboxes(mine blew at 18k miles) service dept was never informed of the cause or preemptive work to be done, they were completely left in the dark by Audi and told a new bax was on the way
3-4 weeks sounds great a friend got his V8 in the S4 in less than 10 days even though none were susposed to exist in the US( the new second one lasted until 44k mi), others waited up to 5mo