Auto Parts: Performance chips, coolant temp, performance chips

Question
I noticed a lot of folks are trying to sell these performance enhancing computer chips for newer model cars. You can buy them for almost any vehicle made in the last ten years or so. I've tried to do my own research, but nobody seems to really know if they actually do what they claim: improve power and mileage. I'd love to hear your thoughts on these chips.

Answer
    I've experimented with "performance chips" since they first came out in the early eighties.  Since OBDII became mandatory in 1994, there have been two basic kinds of "chips."  One is the cheap kind that is sold for anywhere from $25 to $100.  These are all the same, the price is based on the amount of gall had by the vendor.  They attach to the MAP sensor, or sometimes the coolant temp sensor, and  work by tricking the computer into believing the conditions in the engine are different than they really are.  These will not improve gas mileage and will, in fact, make it worse.  They encourage the computer to deliver a richer mixture and a more advance spark.  Combined, these will make more power.  But only a little improvement, maybe 3%-5%, is available this way.

    Then there are the devices that plug into the service port on the ECM.  These are designed to alter the programming in favor of better power while still keeping the stock programming going.  They can cost anywhere from $300 to $900, depending on the car.  Most German and Japanese cars will require a very expensive version.  The advantage to the expensive ones is that they enable you to access the programming through a laptop or built-in display.  If you know enough about tuning for power you can alter spark timing and fuel delivery curves as well as increasing RPM and MPH limits built in at the factory.

    Based on what I have learned I would have to say that use of the cheaper devices is a bad idea.  The improvements will be very small and the danger to the engine from improper spark or fuel delivery is large.  The more expensive ones are worthwhile if you are racing and making significant mechanical alterations (cam, exhaust, ignition box, etc.) to the engine.  If you are looking for them to give a stand-alone improvement, you will be disappointed.  One thing that will give an inexpensive improvement is a K&N air filter.  Don't waste money on a cold-air kit, just buy the K&N stock replacement air filter.  This will give a noticeable improvement in power, one that you can feel in the seat of your pants.  Combine it with a quality performance exhaust (not just a "fart can") and you will enjoy better mileage and power as you improve the pumping efficiency of your engine.