My 86 blazer has a holley 4160 vacuum secondary carb the PO installed. How do you check to see if the secondaries are opening? It is only a 305 and maybe it's because I'm used to running a 350 but it feels very underpowered and I think maybe the secondaries aren't opening. My edelbrock has manual secondaries and I've never worked with the vacuum type. I'm also new to holley carbs. I tried revving it in neutral and they didn't open but maybe it needs a load?