Engine Performance problem
2005 Chevy Lumina V8 Two Wheel Drive Automatic 55 miles
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I have a 2005 lumina ss 5.7L engine. It is a little bit low on power ,my friend has a 2005 lumina ss just like mine but his is faster and has more power than mine. But he had his Catalytic Converters removed for him is that why his car is faster than mine?

mmm, i dont think that will make it go faster. may have some sort of chip or intake. something on his vehicle that maybe he is not telling you, that is not visible

Sometime a good cleaning of the injection system, the MAF sensor, and throttle body helps restoring power to your car.
A new air filter wouldn't hurt either.
Using good quality gas can help too. If you buy the cheapest gas in town, you may need to replace your fuel filter and possibly your fuel pump inlet sock as they may become glogged; a fuel pressure test would tell you that.

http://www.2carpros.com/car_repair_video/test_fuel_injection_pressure.htm