Plog, ehh.. I wouldn't spend the money for one when you can get full blown headers w/3" downpipe for $100 more. Watch the speeddaddy site for their header to get back in stock. $239.99 shipped to your door, can't beat it...
When I had my L36, I ran HAI, 2.5 downpipe (I think that's the size) magnaflow high flow cat, Ubend and resonator delete, stock cat back, no tune, and I got around 280 miles per tank.. 15 gallon tank equates to 18.6 mpg... My foot wasn't that heavy, but my mpg wasn't that great either...
Maintenance, yes all the above. Look at the fuel filter also (don't know if it was mentioned) and seafoam if you want. Headers and FWI will open things up a lil more and you'll be well on your way to a top swap down the road.. ;-)
