Earlier this winter I ordered the VAP crank pulley and tune. I had a couple of hiccups during the installation, but eventually got everything on and installed. Fast forward a few months, I took the car back out on the road and it was hard to get a “seat of the pants” comparison so I took the car to Low Boost Performance in Reno. The attached printout is weather and altitude corrected. The best result was 570 wheel horsepower using a Mustang Dyno. The calculated crank horsepower based on whatever metrics mustang uses was 700. Interestingly, the lower pull was with the exhaust valves closed and the higher one was with them open. Not a huge difference, but the area under the arc is significant. Overall I’m very pleased with the results.

 

I've noticed that I get better lower midrange response with the exhaust in the more open mode. I noticed that even stock.

 

I was surprised. The numbers surpassed what was expected on the VAP website. I realize Dyno numbers can vary, but the guy at the shop said Mustang Dyno’s are “heart breakers” and so he hoped I wasn’t disappointed.