Well of course cars run better with colder air. Its denser. If your X is running sluggish its probably a bad tank like was said earlier, but you might also want to check your airfilter.

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2002 4.6is Dinan S2
Titanium Silver/Black Alcantara

DINAN
Stage 4 Engine Software
Automatic Transmission Software
High FlowThrottle Body
Free Flow Exhaust
Cold Air Intake System
High Flow Air Mass Meter
OTHER
CCFL Angel Eyes
Stealth XM Radio in ashtray : FM Mod
Pilot H3 Fog Bulbs
Cleared Headlights: Hi/Lo Beams
Hardwired Radar Detector
IN PROGRESS
Powerstop C/D Rotors: (on backorder)
W/EBC Red Stuff (F)
W/Axxis Deluxe (R)
Dice Ipod: Aux Input for XM
THINKING
SMG II
MK4
Bluetooth