2000 Audi A4 pulsating idle problem

We have an 2000 Audi A4 quattro automatic with ~ 145 kms ( 90,000 miles) on it. It was recently in to a specialty shop to remedy a pulsating idle issue as well as a power hesitancy out of the hole. When stopped, either in park or at a light, the idle pulsates. The shop invoice reads: Scanned computer interlink and found the following codes: 17522/P114 O2 sensor B1S2 internal resistance too high, 16684/P0300 random misfire, 16687/P0303 cylinder 3 misfire. Smoke tested engine compartment (numerous vacuum leaks detected) requires replacement of vacuum hose under and around intake.
The vacuum lines were replaced but this had no effect on the pulsating idle or power issues.
For those who might be interested, we've had nothing but problems with this car. Engine & differential oil leaks, etc, etc - it's been a real lemon.

Any feedback as to how to resolve the pulsating idle problem would be appreciated.

Stephen

Hey there! I know this is an old thread but for any one else that want's to know, I'd get your car carbon cleaned also a good old service/ long run on the motor in gear 4 doing about 60 might also fix the issue.