Most performance "chips" are totally bogus. They don't increase your horsepower and may actually lower it, besides increasing emissions. Most late model cars don't have a separate "chip" that you can plug into the PCM, the map is programmed in firmware. What they do give you some kind of "module" that plugs into the harness and interferes with the existing map to increase fuel mixture. (sometimes all you get is a resistor that is spliced into the MAF harness and makes the PCM think it'* colder than it is so it allows more fuel flow.) This may or may not increase power by a small amount, but since the stock engine is already optimized, it'* hard to see any benefit. There are also actual computers you can get that interface with the existing PCM on some vehicles to boost power, these are popular on diesel trucks. They increase power by increasing turbo boost and fuel flow, but this is hard on the engine, and will shorten it'* life. In my opinion, none of the junk is worthwhile, on a car especially, it'* very hard to realize any gains without actually modifying the engine itself.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)