dual carb setup help

hi guys just got the car running again tonight, what I have is a early 340 with 10.1 compression extreme energy cam and old offenhauser tunnel ram intake im running two 450 Holley carbs just had the carbs rebuilt by a very well know engine shop in my area now my question is im running a total of 28 degrees of timing at 3000 which I think im going to bump up to 32 after doing some searching the car runs good idling and revs are quick and not sluggish but when I go and drive the car and cruising 30 mph and then go and get into the throttle and it start to pop and bang and falls on its face what do I need to adjust to fix this problem any help would be great my fuel pressure is 6.5 psi thanks