Where to begin...the fuel filter is under the car, near the fuel tank. There is a large cover over the fuel tank, filter, and charcoal canister back there. Go to ECS Tuning (
OEM / Performance / Maintenance / Repair / Replacement Parts and kits for Audi, BMW, Mercedes Benz, Mini, Porsche and Volkswagen - ECS Tuning ) and look up the part, they usually have decent prices on maintenance items. If your car sat for a few months, without having the fuel "preserved" it could have created some varnish in the tank, which may have fouled your filter.
Coils don't generally go bad, they usually just fail. If you aren't getting codes, I wouldn't worry about the coils.
VANOS seals themselves don't make any noise, but sometimes they result in poor quality or low RPM idle, torque surges, especially low in the RPM range, and below-average fuel economy. If you hear a rattle near the front of your engine over in front of the valve cover, you can buy a kit that includes the "rattle kit." VANOS overhaul is a pretty in-depth repair process, but if you want to look into it, the parts are cheap and can be purchased as a kit from Beisan Systems,
Beisan Systems - Products and click on the one for Double Vanos.
The MAF can be cleaned with any over-the-counter MAF cleaner, and the ICV can be cleaned with any Carb and Choke Cleaner. I used the Gumout brand on my car, and it worked great.
I usually stick with ECS Tuning for most of my stuff, as they offer competitive prices on most things, and shipping is generally pretty reasonable. Pelican Parts is another resource, and I've used them a few times. Other places, check out FCP Euro, they have great deals and discounted shipping going on right now.
I hope this helps. Sorry for the wordy reply, I just like to type. LOL