Measuring the cylinder pressure is what needs to be done.
I agree with this. Until you know what cylinder pressure you have, you won't know which way to go for improvements. I'd also ping the builder to see if he can provide cam specs. If it was built with stockish compression (the overbore lowers it, btw, if you use stock height pistons) and he put in a bigger performance cam, then you have a recipe for sluggish response due to low cylinder pressure.
If the cranking pressure is low, the best stealth approach may be to swap cams to one that build more cylinder pressure. more pressure = more power.
However, by all means, dial in the carb and timing. That is never a wasted effort.
Cam:
Brand:COMP Cams Manufacturer's Part Number:SK21-222-4 Part Type:Camshaft Kits Product Line:COMP Cams Xtreme Energy Cam and Lifter Kits Summit Racing Part Number:CCA-SK21-222-4
UPC:036584046622 Cam Style:Hydraulic flat tappet Basic Operating RPM Range:1,300-5,600 Intake Duration at 050 inch Lift:218 Exhaust Duration at 050 inch Lift:224 Duration at 050 inch Lift:218 int./224 exh. Advertised Intake Duration:262 Advertised Exhaust Duration:270 Advertised Duration:262 int./270 exh. Intake Valve Lift with Factory Rocker Arm Ratio:0.462 in. Exhaust Valve Lift with Factory Rocker Arm Ratio:0.470 in. Valve Lift with Factory Rocker Arm Ratio:0.462 int./0.470 exh. Lobe Separation (degrees):110 Camshaft Gear Attachment:1-bolt Grind Number:CRB XE262H-10
