NITROS -- bad O2 sensor? Try disconnecting your computer and such. Perhaps the system is getting outta whack. 180 miles per tank ain't that bad -- I get about 200 and I accelerate hard a lot.
The guages can be inaccurate. If you park on a slope or whatever it changes, and even if you corner hard or floor it a lot, the gas sloshes around.
Or maybe someone is siphoning your tank!?
