Streetmaster 318 vs. Performer for street use

I think Toby nailed it on tuning the secondaries but I'll add a little for other questions. First I've never heard of having to turn out the mixture screws 3 turns. If Holley has that on their website it is probably a misprint. With them out that far it's probably too rich and that's why it stalls when you stab it quickly. It may appear to idle well but will do better if adjusted. Warm the engine up completely and set the parking brake and block the wheels and put it in gear. Double check that it won't roll on you. Better yet get somebody to sit inside to hold the brake on if you can. Go out to the carb and start turning in the mixture screws 1/4 turn at a time alternating from side to side each 1/4 turn. When the engine begins to slow down back them back out 1/4~1/2 turn. in other words you don't want those mixture screws out any further than they have to be to provide a clean idle in gear. You may have to reset the idle speed if the mixture screws were way off. Generally mixture screws on a Holley run only about 1~1-3/4 turns out max. Also do this adjustment on a cool day. That way it won't be too lean when it cools off.

I don't think you'll gain enough performance switching to a Performer to warrant the work involved. It is a dual plane but the streetmaster is a very small plenum narrow runner intake so it builds good torque and generally pulls to 5k or a little more on a 318. My cousin ran one on a bone stock 318 and it pulled to 5k no problem. You might be running lean is why your not pulling good on top. Have you looked at the plugs to see what they look like?

Why are you running 95 octane fuel? If it's a stock low compression engine it'll actually run better on 89 octane because the higher octane the slower it burns. 89 will burn faster and produce more power on a low compression engine. If it's real low compression (like in the 8's) 87 octane should be enough to produce max power.