Nope, gas mileage is similar, too. My stock 340/727/3.23 geared GTS convertible gets a best of 14-15mpg on the highway and 10-12mpg in town. My son's 440/4sp/3.23 geared GT convertible gets about the same. Some of that is due to the "reformulated" fuel we have to run here in California. The GTS used to get 17 on the highway back in the 80s with a 73 shortblock (8.5:1 motor) vs. the more recent with the 70 shortblock (10.5:1 motor)...