assuming everything is functioning properly...it sounds to me like it may be lean...sometimes a bigger squirter will solve it. I had the same problem on my 454. everything was fine, than I swapped the performer intake for a Performer RPM & had the same symptom(Holley 770). I swapped the #25 squirter for a #32...helped a bunch. Still think I may need to jet up a couple sizes to...maybe Ill do it tomorrow. John