so i have a 2002 audi a4 1.8T. I've been through everything about this rough idle which is worse on cold days. It vibrates mostly while in Reverse and Drive. I've been through everything from spark plugs (which are only have 8,000 miles on them), to thinking a coil was going bad (ohmed them out and didn't find anything), to vacuum tube leaking somewhere.
Today a technician that has worked on audis alot told me to check the intercooler tubing at the lowest point which is just behind the bumper on the passenger side right in front of the tire. That tubing is from the intercooler and he told me that on audis especially as the turbo gets older builds up oil in the tubing and eventually it backs up into the motor and causing a rough idle. Any ideas or photos letting me know where the tubing is or if this has helped anyone.
Also I checked the tubing everywhere that I can see it and I can't find anything wrong. Something said something about a valve being bad somewhere. PLEASE HELP ME

Thanks in advanced for the answers