A4 B9 spark plug issue

[Simonb1]

Had an issue with NGK plugs in a 2.0 tfsi the car started to misfire/hesitation over 4k I assumed at the time it was bad fuel because the plugs had been changed at 35k and only done 3000 miles. Local Audi dealer found no fault codes and said the car was OK according to the mechanic after a test drive but you could clearly feel it holding back under load. I took the car to another garage and after a test drive said straight away there was a problem and could see this with VAGCOM. Plugs were changed and problem was fixed but when I returned them for testing to NGK UK as I dont think they should fail after such low mileage they claim there is nothing wrong with them on testing maybe over torqued but they were put in at spec 30nm.
If NGK are correct and the plugs are not at fault then why no fault codes for coil packs etc. ?

 

[hortstoprecap]

Plugs were changed, and the issue was resolved, but when I returned them to NGK UK for testing because I didn't believe they should fail after such little use, they claimed there was nothing wrong with them during testing. They may have been overtorqued, but they were installed at the recommended 30nm torque.

phrazle