After putting my smaller blower pulley on, I noticed my mpg seemed to be getting worse. I reasoned that now, I am getting into boost earlier and therefore upping fuel pressure quicker etc. But on the other hand the motor has 206,000 miles on it and maybe something else was going wrong??? Tested this today. 130 miles at aggressive, high speeds-even more than usual: 19 mpg. Return trip: 65 mph, no hard acceleration: 27.7 mpg! I guess the theory is true. With the old pulley, I would be getting 22 or so with hard highway driving and I could get maybe 27 going easy. Around town, it is hard to get over 20.