make small adjustments at a time stop jumping all over the place with the tune. set the timing at 34 to start and work your way up from there 1 deg at a time. i think you would be surprised if you seen some engines dynoed and seen the power fall off in power over 1deg in time or 1 size in jets. you will never find the tune by making to big of a change all at once. the best advise i can tell you is slow down and it will come changing gears from 4.10 to 4.30 will do nothing. headers may help some but making the car run right will be worth more then a gear or headers. i would put a mech sec carb on it before i spent the cash to replace the gear and headers. just a f.y.i i ran 1 7/8 to 2" step header on a 1000hp small block with 3.5 exh pipes and mufflers.