JBian

Hello everyone
I'm new to this forum. Looks like i can get a lot of useful information. One year ago I purchased an A4. 3.0 that required a ton of engine work. About ten months ago, my engine light came on and I had it looked at and the mechanic told me that it was my Cats that were not funcitioning properly. I spoke to previous owner and he never had such a problem, so I was skeptical. Car has 178K. I do mostly city driving only on weekends so car is not driven much, but last month, I took the car on the highway for the first time and then after a few days, my engine light disappeared for over one week. Afer more city driving it came on again. This past weekend, I took the car for a long trip and last night the engine light went off again. Both times, that this happened, my headlight on warning signal started working again. Any suggestions as to what might be causing this oddity? Electrical perhaps? Anyone have same experience? Your feedback and comments are most appreciated.