78 vette running badly at low revs

[howie]

my vette has started to run really badly at low revs , it pops and splutters every now and again and sometimes almost stops , it seems ok when running fast . I have changed all the plugs , all the plug leads , and the distributor cap , replaced the air filter , and sprayed the carb with carby cleaner , where do I go from here

 

[Vettehead Mikey]

Is the car stock? Sounds like a vacuum leak. Check every connection on every line. Do a compression check.