Orca

I am considering adding headers and a single ram hydraulic steering assist. I have a 2003 Eliminator Eagle 220 XP with a 496 MAG. The exhaust is routed out the sides and I am told there are mufflers installed. I am considering the Typhoon 496 Exhaust System from Hardin Marine. Does anyone know if these headers come with all the hardware for a bolt on installation or are there additional accessories or parts needed. Also any idea what I might expect as far as horsepower increase and mph's? Regarding the Hydraulic steering add on, same question, if I were to buy say the IMCO kit does it come with all that is needed to hook it up or are there additional parts I would need to buy as well? I guess one other question, does the ECU need any re-programming? Thanks for any input..