Mac X Pipe Installed-Few Questions

I installed my X pipe this morning. Napa studs worked great after I went back to Napa cause they didn't thread right and then came home after I found out they are supposed to be tight threading for locking purposes.
Thanks for the heads up on that one guys. :rolleyes:
The hardest part of this install was getting the LF O2 sensor plugged back in. Both hands just too big to fit up there.
Anyways, I made my own sensor extensions from some pigtails I got from work. Those work great with the exception of the SES light that just came on at exactly 59 miles. :(
Sound quality is very nice and smooth. Slightly higher pitch than other Mustangs I am used to hearing. I like the sound. Stock Cat-Back does have to go though and soon.
Performance wise, this thing pulls real strong in the upper RPM's and very smooth getting there too. :nice:
Now for my questions:

It smells like it is running kind of rich. It doesn't have the same smell that I am used to smelling from 5.0 Stangs with and O/R pipe. Is this normal?
Plus, I was able to watch my gauge go from almost full to about 1/2-3/4 of a tank in that 59 miles. Definately not normal. Is it possible that the car is running pig rich and burning all sorts of fuel now?
How can I fix this if so?
 
I was really confused by the smell when I put my BBK X pipe on a few years ago...The first 2 days the thing smoked bad an smelled strange. Raw gas and oil smell after a few days it was gone and i was relieved! :) I have been told that it has to do with the oil in manufacturing that burns off and also the computer relearning so that is why you smell rew gas. Give it a few days and get some MIL eliminators and you will be good to go!