Sad to say it, but as you read this, our project GTO has already been sold and is now in the hands of Mr. Will Carpenter, an avid GM enthusiast with a few mint late-models in his garage. We hope he enjoys it for years to come ... and he tells us the mods aren't over yet! Space permitting, we'll keep you updated on his progress.
For now, though, a couple of final notes on the vehicle. You'll recall that in the November 2005 issue, we mentioned some strange noises coming from under the hood, especially around right-hand turns with the throttle closed. We concluded it was simply the supercharger changing speed as the engine basically idled. But it also made this noise in reverse gear. As it turns out, the noise was 100 percent the fault of the installers (i.e. yours truly): I had adjusted the supercharger intake hat such that it was within a millimeter of contacting the driver side fenderwell! In reverse gear and around right-hand turns, the engine leaned toward the driver side enough that the aluminum intake hat began rubbing the steel fenderwell, making the odd noise we were hearing. A simple loosening and rotation of the hat, and we were noise-free.
Finally, you'll note that we've been saying all along how Vortech's supercharger system makes between 7 and 8 psi. Well, a few months back we hooked up a boost gauge during an interim dyno session and were surprised to see 9 to 10 pounds of boost at 6,000 rpm, with a touch more at the very top. This told us that upping the rpm limiter would be a not-so-good idea at this point, as this would cause the Vortech V-2 to really get into its efficient boost-making speed range and start dumping some serious air into the engine. Thus we have, and will continue to, stick with the stock rev limiter and shift points for the time being. ECS recommended that before doing anything else to this LS1 engine, a water/methanol injection system would be in order. This would add power by cooling the incoming charge of air (and likely allowing more ignition timing to be used), but the primary idea of installing such a system would be to stay safe with pump gas, as it would increase effective fuel octane to well over 100. (Who knows whether that's really 93 you're getting at the local fuel stop?) The proof is in the pudding, as ECS's record-holding, mid-9-second supercharged C5 runs such a water/methanol injection system--and as such is able to burn ordinary 94 octane Sunoco fuel.
Needless to say, there's more power and performance left in this project car, but we're happy with the way it has turned out. Next time you see a black GTO prowling the mean streets of Jersey, beware--it just might be Will Carpenter's 688hp sleeper!
Since the Cat-Back system on the 2004 GTO is so well-supported by rubber hangers, we were able to leave our SLP Loud Mouth system in place throughout the entire installation. Four bolts are disconnected where the stock cat pipes meet the Cat-Back. | 
There are a total of four oxygen sensors on this vehicle, which need to be unplugged at this time. This is easy for the aft-cat sensors, but the two front ones are a bit of a challenge as the harness plugs are tucked atop the transmission. Some dexterous hands and slim arms are needed to access and unclip the plugs. | 
A brace holding the rear cats to the transmission crossmember will not be reused. Just disconnect the bolts holding the brace to the tranny; leave the nuts attaching the brace to the cats alone, as the whole thing will be tossed anyway. |