Hey every one as some of you may know i redid my exhaust a few weeks ago on my 1997 GTP, and put my catless down pipe on its a 2 1/2" ZZP DP on stock exhaust manifolds. I have a P-log just not installed yet. So after redoing my exhaust i got worse MPG's then before, my thought was it was because i had no o2 emulator to think i have a cat. My exhaust set up is 2 1/2" catless DP, thrush glasspack as resonator, and stock mufflers no leaks. So ZZP was kind of slow at getting in my o2 emulator and i been driving around with out it for a while and best i was getting was between 16.6 and 16.8 mpg, before i was getting around 18.6 and 18.8. So today i got my o2 emulator and followed instructions to put it in (pretty simple didnt say anything about disconnecting the battery or anything) so i put it in started my car and same code was there (P0140 o2 sensor CKT no activity "bank 1 sensor 2") so i decided to erase the code, then it went away didn't come back after driving it for 15+ miles. So does this mean its working? But im still getting the same mpg's i dont understand i thought better flow would make me get better gas mileage? Any one have any thoughts on this or can help me out, would be greatly appreciated! And if my o2 emulator is bad i want to send it back ASAP before its to late.