As a new '98 TDI Avant owner with an airbag light on, I was interested to read earlier threads. Can anyone tell me for certain if when the light is on the airbags are not functioning, or is this not the case? Also the car sounds a bit 'boomy' with resonance from the engine (exhaust is ok) and as my undertray is missing can anyone tell me how important it is from a function and sound deadening point of view. Lastly! Can you get replacement foam sheet for the underside of the engine top cover?