Like rb446 said.. a rebuilt double pumper will do more for the "seat of the pants" dyno than almost anything. Trust me I dumped a bunch of money into my old 3310 before stepping up to my 850 double pumper.. bolted on the 850.. felt like I picked up 30hp right off the bat. Truly awesome ! .. but beg ,borrow or steal a double pumper !! You won't regret it. Lol.