My question is , after installing a aluminum intake manifold my 15 engine started fine but ran me out of the shop .The exhaust was really bad . I tried all the fuel mixtures i could think of . Didn't help. The one thing i did notice was that the manifold iced really fast at the elbow. Put the cast iron manifold back on and all is well. Cold but not the ice. So much for trying to get 2 more horse power. Why ? Bill