If your racing and asking about swapping carburetors then you must know about air fuel requirements of a motor. Wideband O2 sensor in the pipe for 5minutes to set up jetting on all carburetors if you have the assortment of carburetor parts Jets, needles, jet needles, throttle valves; see the list.
A person can delete the power Jets just by switching float bowles. If racing you understand the air box is critical to suck uniform cold air from outside source. Uniform in the sence, each carb gets the same cold air intake. The air under the hood is all over the map and when wideband O2 sensor checked you end up chasing tail.
I've yet to see an oil pump fail. Motors at idle need 120:1 ratio of oil to fuel and 20:1 at wide open throttle (WOT). The point to old school thought was to be able to "change jetting" by adding more oil to the fuel; thus less fuel and more oil, but the air fuel manipulated. You'll learn the motor with more oil. AT the expense of fouled plugs.
The horrible clutch chatter is normal. Your bog I expect is your drive belt (get new one). Flooding at idle, maybe fuel needle seat, dirty fuel/carb or idle mixture needles too rich. A water cooled sled should sit and idle until the coolent blows out over heated. Call your spikes question a spike per horsepower and call it a night.