a few questions

I have a 97 Audi A4 2.8Q, the motor is stock for now. only mods so far are the Eibach Pro Kit, Thunderbeam HID Kit, and 19 X 8 FRD 4 on 225/35ZR19 Toyo Proxes FZ4. My question is I have just recently got an oil leak it leaves around 1-2" diameter oil spot after the car sits for a while. I'm not getting any warning lights on the dash. Just a little concerned. Is there any common gaskets that go that I should check first. I also had a CEL that read fuel air mixture, had it reset then ran it on 94 oct gas. have not had the code since. (turns out one of my employees thought it would be good to run it on 87 oct even after I told him to use 94) Thanks alot guys for any help you can give me. I will post some pics soon.

PS My cruise isn't working is there a easy fix for this one. I build air bagged and body dropped trucks for a living so I am not affarid of tools.