Hellcats upgraded by Hennessey Performance have received rave reviews from its customers. Watch customers praise our 900 HP and 1000 HP Hellcat upgrades not only for its impressive acceleration and speed, but also its incredible handling ability. Whether it is the H1000 or H900 upgrade, Hennessey has the ultimate upgrades for all Hellcat engines. It’s easy to see why it has become such a popular choice among Mopar enthusiasts.