[chris vickery]

Les, carburetors are set according to air/fuel mixture which is subject to such things as atmospheric pressure, elevation etc. Not such a big deal today as vehicles use fuel injection systems.
Whenever the fuel to air mixture is changed, adjustments to the carb must be made. Adding an excessively long intake or exhaust alters the typical air/fuel mix. I am sure things would run just fine with such a setup as long as allowance is made and the carb is tuned to suit. Simply adding a fording kit and expecting it to run just the same is highly unlikely without some tuning work.