Prior to 4500 RPM or so, your engine is mostly dependent upon displacement, rings, valve timing, etc. etc. assuming that is all good, the 4500 and up range (where we race), is pumping issues. Every little bit helps.
Things to look for.
Don't use the 28 PCI carb to manifold gasket. Use a 30 pci gasket. (or carefully open up the 28 so that it just BARELY clears the manifold/carb junction when compressed. (an EXACT size match is best.)
There is some play in the carb to manifold bolt fittings. With the throttle open all the way, look down the throat and align the carb with the manifold. (Use your CSI Edge Flashlite
)It's tough to determine without a flow bench, but make sure the throttle plate ONLY goes to wide open and NOT further. For comparison sakes, a 28pci flows in the 110 CFM area. A 1/16" of over or under on the throttle plate can make 5 CFM of difference. (pumping losses)
Obviously, make sure when your accelerator pedal is on the floor that your carb throttle is fully open to the stop.
Head to manifold alignment. Again tough to get precise without a flow bench, but line it up as best as possible. Don't over tighten. If you have the hollow stock gaskets, they can sometimes compress into the air flow.
Intake air filter. Use a good one (K&N, etc.). An air horn/velocity stack can increase flow, but it is very little and assuming you are using one it takes some extra fabrication to filter the air.
NOTE: A 28 PCI will flow BETTER (as much as 1 or 2 cfm) WITH a proper filter vs, no filter or air horn. It gets a little hard to explain why, but basically it is the air that goes by the top of the carb is gone. With a filter, or even just a flat plate around the top of the carb this air makes a high pressure area near the top of the carb that is usable. The only filters that will sometimes hurt a little is the very short ones.
Of course, clean your filter once in a while.
Cold air is denser than warm air. ie. It can hold more fuel charge. Get your air from outside the cowling somehow. At least make sure you have some kind of seperation from the warm air in the engine compartment.
I know I have talked about this before, but jetting is VERY important. You want the precise mix of air to fuel. DO NOT TRY to detemine this by reading the plugs. Anyone who tells you to do this has no idea of what they are talking about. It could only be done by doing a 20+ second wide open throttle run at load and then to IMMEDIATELY stop the engine and pull the plugs at that point. Even that will tell you very little except for a gross error in jetting. You CAN get close with EGT readings, or right on with a Wide Band 02 sensor. (Not one of the cheap $100 ones.)
Typically if jetting is set for your track's altitude (base barometric pressure), you will be close for the full season. Ambient temps and day to day barometric pressure changes will affect this a bit, but without EGT's or O2 readings I wouldn't mess with jetting at the track.
I hope the seasoned guys didn't get bored and the newer guys get some help from this.