NONE. It seems they are pretty much waste of money.==== DETAIL ====I am currently reading Motorbooks "How to tune and modify engine management systems" (Jeff Hartman). And his opinion is that just swapping chips don't work anymore. The factory has pretty much optimized the engine for the best of all worlds. That was really something for the first gen EFI system.If you do find a chip that actually improves the performance, it is because they are somehow flooding the engine with gas. Which means (1) you will probably fail emission inspection (2) lose your MPG efficiency (3) possibly destroy your cat converter.Cars run the cleanest at 14.7:1 air to fuel ratio (at cruise and idle). But cars has the best power at 12:1 AF ratio. So some of these chip will ALWAYS run your car at 12:1 (instead of just when accelerating). So as above you will have problems down the line.==== That was the BAD news ======== This is the GOOD news ====In the future look in to buying a factory turbo charged cars. They are detuned at the factory and can get dramatic increase in HP with just the chip (or ECU) swap. I have an Audi A4 1.8T turbo (150 HP). And I've research this question. With just a swap of the ECU I can get 50 HP. WOW !!! I am not advocating Audi. I am finding it too fragile so I will not (nor ever) mess with Audi again.Good luck.===Don't forget to vote for the BEST ANSWER - please - whoever it may be.FACT: You also get +3 points when you vote for BEST ANSWER