I recently learned about the performance shift ability that earlier GTPs in this generation had. I've also read that the newer GTPs in the generation (ie. 2003) still have the capability with a little wiring to the ecu and an auxiliary switch. However, I've read that for this installation, you need the a DHP reprogrammed ecu. Is this correct, or is this just a marketing scheme? If the installation was done on a non- reprogrammed ecu, would it still have a positive effect on the shift timing? I'm looking into doing it, but I don't want to start if it won't make any difference. I realize that it may not be able to do the
4-2 or 3-1 downshifts without reprogramming, but hopefully somebody has some information on whether or not it would still have any effect.
Thanks for any advice.
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