Hmmm so maybe i should stay with stocl exhaust and get a K&N or should i go Stillen since it still uses an airbox? Or maybe ill just say **** it and get an Injen since that seems to be the most popular with the G35.....I also need to find a place in North FL "Jacksonville area" that can detail the engine compartment.....mines getting really dusty and i hate to let it go for so long. I dont have an engine hoist or my own garage. Apt. living FTW!

Colder air makes your milleage worse actually, becuase all fuel injected cars have an intake air temperature sensor which detects the intake air temps and the ECU adjusts the amount of fuel injected into the motor to account for how hot or cold the air is(colder air when measured at the same elevation generally has more oxygen per measure of air volume than the same air when measured at a warmer temperature). If your car didn't have this, it would be more apt to leaning out in cold temperatures and more prone to detonation as a result.

I've been able to really witness this impact firsthand on my car and truck by using the Scangauge to monitor real-time fuel useage statistics and compare/contrast them with intake air temperatures(also indicated on the scangauge). It's quite interesting stuff... at least I think it is.

I doubt the stock ECU can adjust itself that much. If that was the case, these car's wouldn't be running 15-16 A/F on stock map with 30-50 degree weather. I see what ur saying though.

Trust me, they do. You would be very surprised to see how much the mixture is altered just from temperature alone in modern cars. In my Tacoma(I use this as an example because I drive it a heck of a lot more in the cold weather, so I can give more accurate depiction of just how much of a difference there is between cold and warm weather), over the past 3 years since I've owned the truck, it's gotten an average of 3.7 MPG less in the winter months than it does in the mid summer months. Part of this may be as a result of the different gas mixtures(seasonal gas in the Northeast). The past few days have been unseasonably warm here though, and my fuel economy has gone up accordingly by at least 2 MPG during this unexpected warm spell in comparison to what it got on the same exact type of gas over the past few weeks(winter gas in both situations). I can notice it quite a bit cruising on a flat road at a set speed once the truck is fully warmed up... because the real-time fuel economy is noticeably higher than it usually is when I drive those same roads on a really cold day.

i got increased mgp..i get about 24mpg..with my mods..hopefully it will increase a lil when i put my HFC and tru dual HKS exhasut.

+1 on the ECU using air temp for fuel regulation - just plug in a OBD2 scanner that can scan with the car running - that is one of the first parameters listed. It's there because the ECU needs to know.

as far as having more complete burn? that should only effect the power not the mpg

That was explained already 3 posts above, but thanks.

3 posts above talks about DECREASED milage during cold months .... but hey, you're welcome

i heard that CAI helps increase mpg but headers dont....i dont knoe if its true