My 98' v70 has 178K miles and I was getting about 24 mpg on the highway at speeds of 70-75 mph. After the dealer replace the air pump and related valve, my highway milage dropped to 19 mpg. Any ideas? The dealer says the air pump should have no effect on milage. I ran a test,however, and disconnected the air pump (by unplugging breaker), and my milage went up to approx. 22 mpg. I should also mention that a lot of black smoke came out of the exhaust on initial startup after the air pump replacement. I then replaced the plugs/wires/dist.cap and rotor. This had no effect on milage, but seems to have decreased black smoke.