From what I have read, the 05' GT takes 87 octane gas. Are their any ECU upgrades
that allow for more HP by upping to 93 octane. What does a stock 05' dyno at?

 

To answer your ECU question yes. There are improved timming maps that can be used with higher octane fuels. Higher octane allows more aggressive ignition timing and allows more margin for a hot lean A/F mixture without detonation so you can gain more power. From what I've seen an '05 is good for about 260WHP or so and this is backed up with the typical corrected quarter times most magazines have reported.

 

I tried the high octane gas and didn't notice any difference though the car was still new then. With the price now on a gallon of gas I'm just thankful that I can run 87 octane.

 

Higher Octane just give a small performance, but nothing to beat anyone in a race. And they only way to get a couple of HP from higher octane is to change the computer chip. Right now most chips are like 82 84 and that is what is will accept, put put 94 and only a littler different perforance. Change the cip and you can up the performance.

 

I a recent magazine article (I can't remember which right now), they claimed an increase of something like 3-4 hp, when running 93 over 87 octane. Since that less than 2% of the stock rear whell horsepower, I am not sure it is even real hp gain, or dyno variability. Even if real I doubt you can feel it, in the seat of your pants. lol