4160 Holley help

So I got her running on my 360 now. Seams like I have a little off idle to full throttle stumble in neutral since I can't take it on the street. It only stumbles if the Rpms are at idle. If I load it up even to 1000 Rpms it doesn't stumble. Where do I start there? I also bought a jet kit so pros and cons of using a power valve plug? And where do I start with jetting to compensate for it?