7mpg? wow...i mean when i threw on my LT's no cats I maybe lost 1mpg that was with no tuning/sims nothing and I would assume that was just because of a heavier foot wanting to hear the car more. I definitly dont think I would attribute that to !cats alone...maybe a lazy o2 or something
but even that might not hurt it that bad...my front o2 died on my gtp about 2 weeks ago now & I still was able to get the same mileage out of a tank as usual. Thats with the stock ve/maf/ofla tables.