They're good for about 1-2 hp on the upper end when using a K&N.
They also tend to help out when you live in areas like I do.... It's been over 100 degrees every day for over 2 weeks now...
Other than that, they're mostly cosmetic, but if you can find a good deal on one, snatch it up....
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1998 Mustang GT
13.97@103
"Traction Impaired" or "Nitto Needy"
Pilot Proverb:
If all you can see out of the window is ground that's going round and round and all you can hear is commotion coming from the passenger compartment, things are not at all as they should be.