I have much respect for many tuners out there, but Hennessey is by far my favorite. The build the fastest Dodge Vipers in the world, with kits ranging from 600 to 1100 horsepower, and have won numerous awards in performance competitions. They even beat the Bugatti Veyron in a 0-200 time trial (
Road & Track article). They also have kits and parts for many other cars, from Bentley Continental GTs to Jeep Grand Cherokee SRT-8's (which is tested to be the fastest SUV's on earth (
Car & Driver Article)
Also, I think their cars are drop dead beautiful
biggrin 
HPE website.