I just installed a worked pair of exhaust manifolds on a 454 that previously had headers. The carb is a rochester that was rebuilt by jet performance. The engine ran perfectly with the headers but now seems to be loading up (fuel) and seems to miss slightly when revved. I'm thinking i need to lean a 1/4 turn on the screws. I have timing at 34 total with 14 initial.What do you all think? thanks