This will have a large effect on performance and it will vary will rpm
. Without the cooler, the intake air will be hotter and therefore less dense. There will be greater losses through your valves and the engine will tend to run richer. At low load, this can occasionally be a good thing because it will make your combustion and expansion more efficient. At higher loads, you will not have sufficient oxygen to fully burn the fuel
hurting both power and economy.
Another thing to be concerned with is your EGT's. Without the cooler, your exhaust
gas temperature will be higher potentially to the point of being harmful to the engine. Without a pyro gauge, I would not run without the cooler.