I am using a product called Auot-RX,
http://www.auto-rx.com. As far as I can tell the mileage has not increased any, but its good peace of mind. The engine did start to feel stronger somehow. I'm currently in the rinse phase, using Castrol GTX 10W40, might go back to 10W30, I can't really tell the difference in this engine.
I've got the stock Filter in the engine now, not much dust in these parts. I put everthing back to stock a few weeks ago and sent it to the dealer for a ticking I though I heard. Turns out it was nothing so I put the Borla back on, have not done the filter yet, perhaps this weekend.
The last long trip that I took with the Borla and K&N I did not fill up until I had 316miles with 1/4 left on the tank. MPG came out to be 15.9. Hoping the chip gets me closer to 17mpg. I was traveling at speeds up to 80mph so I think that was pretty good.
