how do you think the gas mileage in the city compares to that of an ls2 gto.. lets say an M6 ws6 with 450 RWHP and 4:10s compare to a stock ls1 A4 GTO? im looking at buying an m6 ws6 and my dad always complains about his gas mileage in his gto.. do you think if i drove his around for a week it would be about the same or close?