You switched from a victor 340 to an action plus and went from 102 mph to 98? Whoaa! Weiand has been known to have core shift problems fairly often, maybe that was some of the loss. I would not expect just the manifold design alone would be responsible fora 30+ hp loss. Anyway... i think the Victor 340 intake may be a little big for your engine and the Action plus just crappy. An Ed Perf rpm/air gap or LD340 might work better in your application. And MORE converter. I don't think your mph of 102 is bad for what you have but your et and 60 ft need work. I would bet that your torque peak is in the 4500 rpm range or higher. Put a converter in that will get you farther into the powerband than the 3500 unit you have now. Little engines like the 318 need all the help they can get off the line. You will launch harder if you can leave at close to the torque peak. A street car can reliably handle much more stall than some people on here seem to think. Just gotta have a good cooler. I have a 9.5 Dynamic that flashes to 4500 behind a worn 440 in a b body that's heavier than your car and has 3.23 gears. Been in the car for 8 years and hasn't burned up the tranny yet and is driven regularly in all kinds of weather. I don't make much power and my mph is only 107, but my best et is 12.35. 60 ft best is 1.69. BTW,you don't need a bigger header.