cranetruck

Jim, get a low pressure gauge on ebay! They are listed all the time, keyword "magnehelic". They go for less than $10 usually and are calibrated in inches of water, cm of water, pascals, psi or other.

Simply run a plastic tube from the air filter canister to the gauge and you are good to go.
I even got a mounting bracket in one deal (see image above).

The capacity of the filter is one thing that should be matched to the engine requirements, but the restriction at a certain flow rate is what makes the difference.

This is my understanding: A higher air flow rate will lower the EGT, permitting more fuel to be burned, which in turn equals more power. So if there is enough air for the fuel to burn without exceeding an EGT of 1,200 F, then more air wouldn't do anything unless the fuel was turned up also.

Bjorn
Virginia's Blue Ridge Mountains
Avatar: XM757 in OK prepared for 1,000 mile trip home. Part of 6,000 mile journey in 2006.
1968 M49A2C modified with 1960 M756A2 truck bed and 1975 HIAB 765A knuckleboom. Heated dual tank system for biodiesel/veggie oil use.
1969 Ford XM757 8x8 5-ton truck tractor W/W, the "improved" MV.
"Some things can't be made better, just differently......a lot of things actually"