RE: Does an SCT dynotune eliminate the need for a chip?
It depends on the car. On EEC V cars ('97-'98) they can flash the computer, but most tuners will be using chips anyway. On earlier cars they need to use chips. Which is why most tuners use chips on all cars, so they don't have to pay extra for the chip burner and the flasher.
Your car should still retain trouble codes with an SCT chip. I don't think i've had any since i got mine though.