Carb problems help Don, anyone

[mkcobra]

I have a mildly modified 351W with eldelbrock heads, 750 carb, and MSD dist should be making right at 400hp per Dyno sheet. Don i think this is your standard 351W setup. i ran it on the Chassi dyno and found a problem, it doesnt make HP. infact it seems to jump to 215 hp at 3200 rpms and then only climbs to 244 by 5800 rmp almost flat. it does seems to pull strong on the road but not like a 400 hp motor would. it also seem to struggle when the rpms go up. any ideas, fule mixture is very weird also starts at 13 then drops at 4000 to below 10 then back up to 12 at the very end. almost looks like a large V shape not like any other curves we have seen. i am questioning the carb like maybe the secondaries are not opening. I am a little new to elelbrock can you adjust the secondaries to open and when. its a model 1407, heads are the 6025 aluminum. any help would be appreciated.

thanks