rough idle not fixed

hi, i have a 99 A3 1.6 with 75,000 miles on the clock, i have had the car 3 months and is still under warranty, the car had (and still has) a rough idle, has had a new inlet manifold, throttle body and MAF sensor which was all covered by the warranty, however, changing all of this hasnt fixed the rough idle, no faults come up on diagnostics and there are no engine fault lights on the dash, is anyone able to shed any light on this as the mechanic and myself are running out of ideas.

Cheers
Joe

anyone?