With the stock airbox out of the way, it was then time to step up our game to a full air induction kit. Since K&N happens to offer two intake kits for the LS2 GTO, we figured it was worth giving each a try. The first system is the Typhoon kit (part number 69-7201TP, $321), which uses a polished section of aluminum pipe that is connected with silicone fittings to the mass air meter on one end, and the throttle body on the other. It includes an air dam that prevents hot air from the radiator's cooling fans from getting into the engine through K&N's trademark stack-style air filter that sits right behind the driver-side headlight. With it bolted in place, we found a sizeable gain of 12.4 hp and 6.7 lb-ft of torque at the wheels, compared to our dead-stock baseline. Considering that K&N only rates this kit at a 10.25-rwhp gain, we'd say that they are being 20 percent conservative. So, our new power peaks were 347.3 hp at 6,100 rpm and 336.8 lb-ft at 4,700 rpm at the wheels.
Not wanting to stop there, we then sampled Summit Racing's high-flow mass air meter designed specifically for all LS2 engines. It is the same size from the outside, but it modified for increased airflow and is retuned for more performance. Installation was a five-minute deal and once we were finished, we managed to wrangle 352.9 hp at a lower 6,000 rpm, and torque took a nice-size bump upward to 340.0 lb-ft at a higher 4,800 rpm. The air/fuel ratio was still safe at 11.64:1, which incredibly, was a bit richer than on the baseline run when the car was bone stock (11.93:1.) This translates into a gain of 5.6 rwhp and 3.2 rwtq over the stock meter when equipped with the K&N Typhoon kit. Airflow is certainly making a positive effect on our Head Poncho.
With plenty of dyno time still on the clock, we then tossed on the K&N FIPK system (part number 57-3053, $285) and retained the Summit mass airflow meter since we liked what we saw. With just the simple change from aluminum to HDPE piping, we were now looking at a dyno sheet that said our GTO was making 352.7 hp at 6,000 rpm and 341.4 lb-ft at 4,800 rpm at the wheels. So, the FIPK was just as good as the Typhoon intake as it stayed within 0.2 hp and 1.4 lb-ft of torque. On our project car, the difference was a wash, so either intake kit would work equally well. It would simply be a matter of personal taste as to which one would suit you better for looks and budget.
Plugged In To Performance
Our next item to test at SLP was its handheld tuner, sourced from Diablosport. Its Predator handheld unit is one of the most sophisticated on the market and, because it is an SLP-specific piece, it comes with several custom tunes already programmed into it to complement its own line of Bobcat performance packages. Because our Head Poncho did not have a Bobcat engine package, we were still able to take advantage of the Predator's innate abilities to alter fuel and timing tables for more performance and increased fuel economy. It took about three tries, but once Hank figured out what our GTO liked, we were able to find an additional 4.8 rwhp and 5.8 rwtq for a new peak of 357.5 rwhp at 6,000 rpm and 347.2 rwtq at the same 4,800 rpm.
 SLP offers a specially programmed...  SLP offers a specially programmed version of the Diablosport Predator tuner (part number 27010T, $489) to match its own line of engine packages for the GTO. While our car was not so equipped, we were still able to use a performance tune from the Predator and, in just two tries, we were rewarded with 4.8 hp and 5.8 lb-ft of torque at the wheels. Certainly worth it, especially if you intend to make future modifications down the road, such as injector size changes and tire size adjustments. |  SLP's underdrive pulley for...  SLP's underdrive pulley for GTOs is a piece of billet steel perfection. With a new pair of accessory drivebelts and new bolt (shown) we were ready to see what kind of power gains were to be had. |  With the stock pulley removed,...  With the stock pulley removed, the difference in size is apparent. By slowing down the speed of the driven accessories, more power can be realized at the wheels. An added benefit is the reduced centrifugal weight that the crankshaft has to spin thanks to its smaller diameter. |
 Once installed, the SLP pulley...  Once installed, the SLP pulley provided us with a sizable gain of 7.7 hp at the wheels and 2.7 lb-ft of torque with no detrimental affect on driveability. |  Next up, we removed the stock...  Next up, we removed the stock cat-back exhaust from our Head Poncho and compared it to the artful 3-inch system by Stainless Works-the stocker looks like a purely agricultural piece of ironwork. |  To install the new Stainless...  To install the new Stainless Works cat-back exhaust, simply clean the mounting flanges and lift it into place. With all the pipes aligned and the provided band clamps tightened, we checked for leaks and made a quick run on TTP's DynoJet. |