Originally Posted by whatredline
sorry i forgot to specify but they are both non turbo. I'm going to go with royal purple all around and im wondering if it will make a difference.
Not really. Most folks will advise you against synthetics in the motor. Unless it has been tampered with, there should be a oil metering pump that injects oil directly into the combustion chamber to lubricate the rotors. If you search a bit you will find pro's and con's in other threads (regarding injecting the synthetics into the motor) that explain it better than I ever could. The consensus here seems to be running Castrol GTX 20w-50 in their engine. Don't forget the LSD additive for the lsd when you are changing it (if you have a GXL).
As for basic mods i'm assuming you mean power adders. Since you already have an exhaust you might as well go for more bolt-on's and get an intake and header. I'm happy with my K&N cone filter, but if you have an S4 you'll need an adapter to bolt it up where your stock air box used to be (S5 you don't). As for headers you'll have to search to find the best for your application as price and build vary from manufacturer. Some have a bung to help in the activation of your auxiliary ports if you plan on deleting the cats (again, only necessary on the S4).
Other than that, do a 60k tune up (plugs, wires, fluids, etc...) and you'll be a lot happier in the long run and get a bit more familiar with the 7. Keep up on those oil changes and you'll get a lot more longevity out of it as well.
Other than that, there's a lot you can do regarding brakes, anti-sways, tires, and power. Your best bet is to use the search function as there are a lot of threads covering most of these topics already.
Here's a few sites to help you if you want to do some online pricing....