Very good for the price
Installed in about 2 hours on a 2002 Olds Bravada with a 4.2 engine. (My first one) No air leaks or squeals so far. It does give it an extra "Punch", but not as much mid-range as I was looking for. (My other car has a V8. Guess I'm spoiled?) I can definately tell that the engine is not working as hard at speed, and have seen around 2-3 more miles per gallon on the highway. In town mileage is about 1/2 mile per gallon more...only if I keep my foot out of it. Once the car's computer got used to the unit it mellowed out the sound. It's still much loader and throatier when you punch it. I don't tow much, but it seems to have more low end torque which should help when pulling a load. Overall I'm very pleased with the outcome.