an intake won't improve mileage with a tune. a tune in itself might but unless you're running at wide open throttle it isn't going to make any difference. at WOT these cars are tuned a very rich AFR but at normal driving the front O2 sensors keep the air fuel ratio at stoich (14.7 #s of air to 1# of fuel) no matter what the tune. also the more cold dense air you pull in will cause the computer to also bring in more fuel to keep the ratio the same. you may have the gas pedal not quite as far down to maintain the same speed (it would be imperceptible) but you're burning the same gas. the only way any kind, including stock, would be affected at normal driving is if the filter is plugged.
an intake that lets in more air at WOT burns MORE fuel keeping the AFR the same and thus makes more power. i have the data of it with different intakes too using MAP (manifold pressure) which relatively shows how restrictive different systems are. LPE and K&Ns give about a 4 kPa pressure drop at high RPM WOT runs, Volants are worse. the stock box is even worse with a 6+ kPa drop over 6,000 RPM. my direct shot OTRCAI averages 1.4 kPa over 6,000 RPM
2004 Blk/Rd M6 (Ziggy) 12.34 ET, 113.55 MPH, 1.82 60ft
Go: DIY OTRCAI - SD tune - HPT w/LC-1 - SLP LTs - FTI SS HT Cam - Stiffy - SLP UD - 243 Heads - Custom Exhaust - NW 102 TB - FAST 102 - 3.91s w/Spring Kit - DiffTech DS - Fjord 42# Green Tops - Diamond Stg 3 clutch
Handling: GMM Rip Shift - Harrop Cover - Koni's - Hotchkis - Lovells springs - SuperPro - Energy Susp - Pedders - '05 Brakes - 1" widened rear wheels
Show: Tints 55% Fronts, 15% Rear & Rear Sides - '06 Black Tails
Last edited by svede1212; 09-28-2009 at 07:02 PM.