you may get better milage once the car breaks in a bit more. i know its probably broken in mile wise but it will get a bit smoother. i checked the air in my tires and they were a few psi low in front and back. got them back up to 32 front and 29 back. still doesnt solve my problem as to why my car is so close to boost when cruising on the highway and applying no gas at all. never used to do that........the needled on my boost guage is almost at zero all the time on the highway. it used to say well far away from making boost.

 

if im cruisin around 75mph in 5th I will usually hold 10in vacuum when the road is flat

If I didn't drive mostly city miles and the roads were flater I would probly get better then the 200/12gal im use to. Going on less spirited drives would also help.

I definatly agree that taking the engine to 4k before shifting is best. Unless its the 4th-5th shift which I let go till about 4300 or so. Its the only way to stay off boost and still move at a decent rate of acceleration

 

guack mine would stay about 10-12in vacuum too on highway at 75-80mph. now its at like 4. its right below 0. i can almost see my gas needle going down as i drive on the highway. my tires are inflated, my boost controller or anything else has not changed on the car. i used the shell gas maybe that is making it want to boost a little more??

 

it might be because its colder out. i know you ge worse boost spkes in the colder weather so you probally get more all around boost

 

I'd check the tire presures (as mentioned above) and also ask to see if the station you fill at has switched to a winter gas formula. Where I live they have to add ethanol in "winter gas" per a state statute. The stuff really kills my fuel mileage.