I have a fresh 355 with a mild build (355 hp, 390 tq.) roller cam, 9 to 1 compression, air gap intake manifold topped with a Holley 4150, mechanical secondaries. Vacuum is at 16 inches, idle @ 750 rpm. Idle is great and the engine runs strong and smooth. The engine is in a '79 Corvette with a manual transmission. When cruising on the highway, if I accelerate lightly there is a bit of a stumble. I have been doing a bunch of internet reading but this is where I come for the answers I trust. I am leaning towards the primary jets being too lean. At first I found that the accelerator pump was out of adjustment and I have that back within specs (as far as I can tell) and it has helped a lot - but the stumble, though less noticeable is still there. Your thoughts as always, are appreciated.