Is there a BIG difference between HP exhaust manifolds(68-70) and the 73 manifolds that came with my 340. Seems like I get a lot of answers ranging from a LOT of flow to just 1-3/5 HP . If its just 1-5 HP I would not waste the $$$ on HP manifolds. I was looking for actuall tests or test results becuase ive gotten so many differing oppinions I don't know which is right but at least with actuall test/dyno results there would be something concrete to back it up. Someone had said Mopar Muscle did a test(between stock 318 manifolds,later 360 manifolds,HP manifolds,Shorty headers and full headers.) but I cant find the test anywhere.