Their return policy is very bad and they charge a huge restocking fee. When they claim it helps on gas mileage, it's not true. Beware - You should not clip the signal wire of your oxygen sensor, which they're suggesting you clip, They're twisted and you can do damage. That's what a Chevy guy told me and I'm glad I listened to him. We did not cut the wire. Don't buy their products. All the way around, they're bad, bad, bad. read full review »