So how much horsepower can a tune and a new air intake on a 2007 Shelby GT500 net you? How does 505 rear wheel horsepower sound? VMPTuning, a company based out of Debary, Florida, specializes in SCT Tuning and has taken a 2007 Shelby GT500 Mustang, with just a tad over 1,000 miles on the odometer, past the 500 rear wheel horsepower mark with a tune and a custom fabricated air intake system. After running the car 3 times on the dyno in stock form the car was able to put down as respectable 421rwhp/438rwtq, 424rwhp/427rwtq, and finally 419rwhp/422rwtq.

So how does the stock tune fair? According to Justin, the person responsible for tuning the GT500, it is a huge disappointment.

The stock tune has no timing in it at all, it’s really quite disgusting. With the stock tune the air/fuel came in a little lean below 2000rpms, ran 11.5 through the mid range, and hit high 10s past 5000rpm. The car makes about 9psi of boost in stock form, just like the guage on the dash says. With the stock airbox the MAF is almost pegged, reading 4.95v.

After the tune he quickly ditched the stock air box in favor of a VMPTuning Air Intake.

I whipped up a prototype intake the night before with parts I had laying around. I took a piece of 4.5″ aluminum tubing, a 4.5″ cone filter, and a little CNCed aluminum flange that I had made a while back. The flange allows you to mount a slot style mass air sensor into a tube. It wasn’t much, but it would give us something to play with. We had to retain the stock tube that passes between the Strut Tower Brace and valve cover. The tube is rubber with a plastic insert to keep it from collapsing, I’m sure it’s restrictive, just like the stock airbox and panel filter. An aftermarket tube with thinner walls would flow a lot more air and still fit between the valve cover and STB.

The air intake required some tuning because the mass air sensor was installed in a new tube. This totally throws off the air/fuel and requires that the maf transfer function be redone, however an experienced tuner can do this in a few pulls. With the prototype intake the car made 505 RWHP/487RWTQ. Simply amazing, with the new intake the car picked up a slight amount of boost past 3500rpm, about 1psi peak at 6000rpm. The sensors were still measuring a little bit of intake restriction though, so the rubber tube between the maf housing and throttle body definitely has to go. I ordered a piece of 4.75″ silicone hose, but it did not arrive until after the dyno testing was done today.

More information on the tuning and dyno pulls: VMP Tunes the 07 Shelby GT500… 505 RWHP