These are well made headers but they wont fit a Crossfire without a lot of modification. I had the V8 version of these (Top Speed) headers on my old ML55 AMG. They made an extra 45hp at midrange and about 13hp extra at the top end. I think it would cost more to purchase and modify them (as the rear angles are all wrong) then to buy a bolt on set from Needswings. The log style headers are a bit of a compromise but they fit well and make good power. I think they are definitely worthwhile.