http://www.europeancarweb.com/tech/projectcars/epcp_1107_project_porsche_gt3/index.html

part of the article:

a significant 13.3 whp and 9.9 lb-ft; this was equivalent to the manufacturer’s claim within a reasonable scientific error. So the Akrapovic Full Evolution exhaust system truly makes power. The graph shows the Sport mode comparison with the baseline run plotted in blue and the final dyno run in red. These results show a healthy curve with 10-13 whp and 15-30 lb-ft gains on the low end, a minor dip in power and torque from 2950 to 4300 rpm (not as pronounced in “Normal,” i.e., non-Sport, mode), and excellent 10-20 whp and 10-15 lb-ft gains upwards to the 8500-rpm redline.

Read more: http://www.europeancarweb.com/tech/projectcars/epcp_1107_project_porsche_gt3/akrapovic_full_evolution.html#ixzz1RV4x9eaN

 

Nice but personally I'd go with Akra's Sport Cup system, which keeps the stock cats, makes almost as much power, costs less, saves more weight, and avoids the CEL issue.