recently replaced a 383 hp engine with another. When I took the old 383 out, obviously pulled the exhaust manifolds off. Didn't give them much thought as the plan was headers for the new engine. Reason for the change was the 383 was not running well at all and couldn't get out of its own way..should also say 906 iron heads that had been redone and oversized valves and med cam. Fast forward to yesterday. Looked at the numbers off the old e. Manifolds. Looks like the drivers side is an actual hp but the passenger side numbers show its a regular manifold not an hp (magnum) That all said, here's the question(s) What if any performance issues would I have been experiencing with different manifolds? Would we have noticed any difference at all? Thanks!