[PonyRunner]

Ok I have been messing with this for almost two weeks now and no luck on my problem. i have a 72 mustang with a 69 351w in it and i recently bought a Rpm Air gap dual plane intake mani and a holley 675cfm carb for it. I put it all on and started trying to tune it. All i get is on a smooth acceleration it runs smooth and idles fine starts first crank but you stomp it and it dies and pops and backfires sometimes. I have tried taking it to a person (actually a few people) Who are carberator axperts as they put it. I have checkd timing, checked valve clerances, set carb many times (air fuel, flot levels, accelerator pump), I checked the timing advance vacum and it was something like 25 on my gauge and nothing seems to change it. I have noticed the secondaries are not opening. So as a test i put my Holley 650 back on and it does the same thing. What could cause this problem? Is that mani too much manifold for this motor? It is the one that Jegs recomended and a few other people did as well. please help me fix her.......

[GTXRacing]

Check your power valve, seats, choke plate (Mine is off) choke timing,
discharge nozzle, secondaries, adjust the fuel flow, jets...

Do the frist time setup procedure and nare it down.