hi i have a 96 sts with a 140k. i just cleaned my throttle body about a week ago. and lately i have noticed when i give it a little gas my instant mpg is lower than it was before. it seems to have more torque (power) though. any ideas why i would be getting worse gas mileage now. and my avg. mileage is now hovering around 18mpg compared to around high 19's-20 before.